tag:blogger.com,1999:blog-45722863633994969632024-03-18T16:56:31.719-08:00Deep Cold: Alaska Weather & ClimateObjective Comments and Analysis - All Science, No Politics
<br>Primary Author Richard James
<br>2010-2013 Author Rick ThomanRickhttp://www.blogger.com/profile/03946704894714514716noreply@blogger.comBlogger2063125tag:blogger.com,1999:blog-4572286363399496963.post-58412256581283006982024-03-13T17:57:00.003-08:002024-03-14T17:07:25.168-08:00Sustained Wind ChillLong-time blog readers will recall many previous comments about wind chill at Howard Pass in the Brooks Range. It's a notorious location with the unusual climate characteristic that the windier it gets, the colder it gets, as low-level cold from the North Slope gets funneled through the low pass (only 2062' elevation) from north to south. We know this because of <a href="https://www.gi.alaska.edu/alaska-science-forum/howard-pass-extreme-inviting-place">instruments maintained by the National Park Service</a>.<div><br /></div><div>The past few days have seen a prolonged episode of hefty wind chill at Howard Pass: at or below -60°F since Friday evening, or nearly 120 hours.</div><div class="separator" style="clear: both; text-align: center;"><br /><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhwZJSSBjTjQ3cy11gTav0QGJ2gSD3EOSZmiqtRKYVxWeAoZix9f1CVolATh2exBVRiylTmL7ZlBtG8nImdI3nt6kCS6yEhKspuGmA2WB2e_pAvaYOZLZ3grwAl3MWIvwk0OnozfdX8YwmBTncJoMUII_knwCttRKDU8-rdRYWPuVRj6-eEdv_3t4Jg1TQ/s1200/HOWA2_windchill.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="1200" height="266" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhwZJSSBjTjQ3cy11gTav0QGJ2gSD3EOSZmiqtRKYVxWeAoZix9f1CVolATh2exBVRiylTmL7ZlBtG8nImdI3nt6kCS6yEhKspuGmA2WB2e_pAvaYOZLZ3grwAl3MWIvwk0OnozfdX8YwmBTncJoMUII_knwCttRKDU8-rdRYWPuVRj6-eEdv_3t4Jg1TQ/w400-h266/HOWA2_windchill.png" width="400" /></a></div><div><br /></div><div>Temperatures have hovered in the range -22°F to -32°F, with sustained winds of about 30-45 mph. Howard Pass has seen much worse in the past (search the blog archives), but this episode is actually the longest on record with wind chill remaining continuously at or below -60°F. The previous record was 105 hours in February 2013, the first winter we have data for. Also, late November 2021 saw 10 straight days with an average wind chill below -60°F, but with higher daily maximum values. [But note that the Howard Pass instrumentation was knocked out by severe conditions in a couple of winters, so there may have been more prolonged episodes that weren't recorded.]</div><div><br /></div><div>[Update March 14: the wind chill finally rose above -60°F at 1pm today, so the new record is 136 hours.]</div><div><br /></div><div>As in every other case of severe wind chill at Howard Pass, the wind has been continuously out of the north-northeast, i.e. perpendicular to the mountain range. The second graphic below shows the location:</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgbxniuweqYVx-AsGVzNjhTJsqRjxZJvaoTjiIlhOurcwg4MmUh-UT3okPiAOQI6s1egv-Jt1kAkJohffaTqEVnDcQ-Q9ZhiEOj6zqOfu-QBSltPadZm-zV1bthjmyalPN-geDNaPf_kAaw1w_vU6VbI_GybW6b5RK1AFedv8mIaxOZybryMRtcM2-x5ag/s1200/HOWA2_wind.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="1200" height="266" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgbxniuweqYVx-AsGVzNjhTJsqRjxZJvaoTjiIlhOurcwg4MmUh-UT3okPiAOQI6s1egv-Jt1kAkJohffaTqEVnDcQ-Q9ZhiEOj6zqOfu-QBSltPadZm-zV1bthjmyalPN-geDNaPf_kAaw1w_vU6VbI_GybW6b5RK1AFedv8mIaxOZybryMRtcM2-x5ag/w400-h266/HOWA2_wind.png" width="400" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEieqp9OxnndBeMYgma40v4nUrQYqc_hXoOHBI_JPyvbcRK4aawONIVRNujvumv39Gj2AkULbhvrL9SCVWeQKrtryeuTu4LlE48sUzW8iBJ8riZK55-MAhRd5IRNTB_dhePsF8Yji4FL2oq0ZL5DvtoAOtxUOk2h5_JaDPfXHOsW7auM4GODqL4gjIqoIow/s1338/howa2_location.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="876" data-original-width="1338" height="263" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEieqp9OxnndBeMYgma40v4nUrQYqc_hXoOHBI_JPyvbcRK4aawONIVRNujvumv39Gj2AkULbhvrL9SCVWeQKrtryeuTu4LlE48sUzW8iBJ8riZK55-MAhRd5IRNTB_dhePsF8Yji4FL2oq0ZL5DvtoAOtxUOk2h5_JaDPfXHOsW7auM4GODqL4gjIqoIow/w400-h263/howa2_location.jpg" width="400" /></a></div><br /><div>Actual temperatures on the North Slope have been very cold: -40s for overnight minimum temperatures in many locations since Sunday, and even below -50°F at the Umiat HADS site (the Umiat RAWS isn't reporting). The Deadhorse ASOS reported -46°F on the 11th, which ties the coldest so late in the season since 2012 (when it was -49°F on March 16th).</div><div><br /></div><div>The MSLP analysis from Sunday morning shows a very typical setup for North Slope cold and Howard Pass wind chill: high pressure draped across the Arctic coast, and a significant (but not extreme) north-south pressure gradient across state. The bunched isobars across the Brooks Range (to the north of Bettles, circled) highlight the potential for strong winds in the mountains. Click to enlarge:</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjVZ_TehAHn8WNWie3haV8DpkaKqnclz84dEXEJM3zytf_VylSx33W4L-xfV0CaZMG73IuhRvCy9rOhvC25U_kRD84_DhlDROluAayKMvU40MxDEt3W9nKPk5lAUXt_k_rPJ1yziW7mdexi6LXU7SAGNlOz7jDwliZ5sxcIzuF4c5gbed8l8tFziWpAWZY/s917/mslp.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="824" data-original-width="917" height="288" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjVZ_TehAHn8WNWie3haV8DpkaKqnclz84dEXEJM3zytf_VylSx33W4L-xfV0CaZMG73IuhRvCy9rOhvC25U_kRD84_DhlDROluAayKMvU40MxDEt3W9nKPk5lAUXt_k_rPJ1yziW7mdexi6LXU7SAGNlOz7jDwliZ5sxcIzuF4c5gbed8l8tFziWpAWZY/s320/mslp.png" width="320" /></a></div><br /><div><br /></div><div><br /></div>Richard Jameshttp://www.blogger.com/profile/08313902028896263276noreply@blogger.com11tag:blogger.com,1999:blog-4572286363399496963.post-5432454610038566372024-03-08T18:21:00.003-09:002024-03-08T18:21:59.186-09:00February Climate Data<p>Climate data for February has arrived, showing that it was a warmer and wetter than normal month overall for Alaska. Both December and January were slightly colder than the 1991-2020 normal, so February was the only month of climatological winter that was on the warm side; but actually all three months were quite close to normal statewide.</p><p>As is often the case, of course, "near normal" masks a lot of spatial and - in this case - temporal variability, as Alaska started and ended February with well below normal temperatures. Here's the UAF statewide temperature index for December through February:</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEir4_PWz_Y-gUaSWJPv6gkUeyZEdAKn4FKb8Er9T7EAjf9Qw80lNcL9W6uLAxAXTuKUZ6F1TKM8jFvfB6cp_KYxnNLftI1yca-Wf-hhfYhdwUWaQTD7kWi8PRvPFqOuLCf0e-vXmYJTow0HWmC2M5qJoMAw-Dq4S29D7cEQ9oxzgmrkYiIR0bRhytJZpFo/s2000/Statewide_Temperature_Index.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1300" data-original-width="2000" height="260" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEir4_PWz_Y-gUaSWJPv6gkUeyZEdAKn4FKb8Er9T7EAjf9Qw80lNcL9W6uLAxAXTuKUZ6F1TKM8jFvfB6cp_KYxnNLftI1yca-Wf-hhfYhdwUWaQTD7kWi8PRvPFqOuLCf0e-vXmYJTow0HWmC2M5qJoMAw-Dq4S29D7cEQ9oxzgmrkYiIR0bRhytJZpFo/w400-h260/Statewide_Temperature_Index.png" width="400" /></a></div><p>For February as a whole, colder than normal conditions were confined to some parts of the eastern interior, whereas western Alaska and the North Slope were significantly - but not dramatically - warmer than the baseline of the last 30 years.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi7h5ZkCP4hvctZHzoD6yEYzZBwnIk96ScHppOuGPnflA1V3i7Je4iDpsv13-jr19QQb30zKJ1hSn1MtHRmJSz63ryR8nMkj38InTWyPmI2IUS6QYvyqOS-K24tel0iMFVVnsHRr4jxFIXivcJFAeToVzD0Hd_B1NKPoWnphksUqcPAaxeA3yYceGdMit0/s770/akt2m_2024_2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="770" height="311" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi7h5ZkCP4hvctZHzoD6yEYzZBwnIk96ScHppOuGPnflA1V3i7Je4iDpsv13-jr19QQb30zKJ1hSn1MtHRmJSz63ryR8nMkj38InTWyPmI2IUS6QYvyqOS-K24tel0iMFVVnsHRr4jxFIXivcJFAeToVzD0Hd_B1NKPoWnphksUqcPAaxeA3yYceGdMit0/w400-h311/akt2m_2024_2.png" width="400" /></a></div><br /><p>The temperature rank map for Dec-Feb shows a moderately significant cold anomaly in the eastern interior, but more significant warmth occurred across the North Slope and Southeast Alaska.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjHRasYleS2OlkstW9l4AL-MiKOOENY9ahRFYW54QuIY7CQpXwNi5ioM9XX-LwqMhoUA3afmdHcsEHOvILy7SV92EeZZF1-yFYZCRv5reva-7D8DfhiHLTuTo5Zz-zcVAK_x4B6KGXF2q99pURa-lUB1GygWRD6Yq0UbV8A0GwCA0vnu8FZuF2X4jgb9Io/s770/akt2m_2024_DJF.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="770" height="311" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjHRasYleS2OlkstW9l4AL-MiKOOENY9ahRFYW54QuIY7CQpXwNi5ioM9XX-LwqMhoUA3afmdHcsEHOvILy7SV92EeZZF1-yFYZCRv5reva-7D8DfhiHLTuTo5Zz-zcVAK_x4B6KGXF2q99pURa-lUB1GygWRD6Yq0UbV8A0GwCA0vnu8FZuF2X4jgb9Io/w400-h311/akt2m_2024_DJF.png" width="400" /></a></div><div class="separator" style="clear: both; text-align: center;"><br /></div>Fairbanks was colder than 8 of the 10 past winters with a Dec-Feb mean temperature of -5.5°F, but that's only slightly below the 1991-2020 average of -4.4°F. On the other hand, Utqiaġvik had its 3rd warmest winter on record (only 2016-17 and 2017-18 were warmer).<p></p><p>February precipitation was very high in southwestern Alaska, locally over 300% of normal according to ERA5 data, and this was caused by a persistently strong Bering Sea trough:</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjDVcZR5jP1iyYC8woalD0kQADq-nRnCP_lJqOKeQbuv_wlIcAEEqiAJtlDdkCWLljslZuTMZYouBRDA1JEtGVJkXP4Tzv5f06s848Sx4OYaZtVaqir1k2jC-7AYbNKgzfxkKgTQUbuQ9DM7ZylHI5f3LIgnOQ86Sg27_kUh1Nph2YgRFEUSgtLsLcDDKc/s770/akpcp_2024_2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="770" height="311" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjDVcZR5jP1iyYC8woalD0kQADq-nRnCP_lJqOKeQbuv_wlIcAEEqiAJtlDdkCWLljslZuTMZYouBRDA1JEtGVJkXP4Tzv5f06s848Sx4OYaZtVaqir1k2jC-7AYbNKgzfxkKgTQUbuQ9DM7ZylHI5f3LIgnOQ86Sg27_kUh1Nph2YgRFEUSgtLsLcDDKc/w400-h311/akpcp_2024_2.png" width="400" /></a></div><div class="separator" style="clear: both; text-align: center;"><br /></div><div class="separator" style="clear: both; text-align: center;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj8OxgEtgY7JnIscgsL7bgWJXtKjJZWaNJOezcR6lDOlNHrDmtbS7DtY5Nbhe1_gFSPQOk_EogRpCD4rak8ZY2YNiWqhra-jfrezXSfTfGOpV6fW9aZAMSHHeFHt1W6R9Y_NPJzHsH1DaNXJkrtZY6jqLKqdc7k1B5SBFEEzdm6OqCeeseO5dhIAE-k7xU/s1027/ERA5.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="688" data-original-width="1027" height="268" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj8OxgEtgY7JnIscgsL7bgWJXtKjJZWaNJOezcR6lDOlNHrDmtbS7DtY5Nbhe1_gFSPQOk_EogRpCD4rak8ZY2YNiWqhra-jfrezXSfTfGOpV6fW9aZAMSHHeFHt1W6R9Y_NPJzHsH1DaNXJkrtZY6jqLKqdc7k1B5SBFEEzdm6OqCeeseO5dhIAE-k7xU/w400-h268/ERA5.png" width="400" /></a></div><br /><div><br /></div><div>December and February weren't particularly wet over the southwestern mainland, but February made for a much wetter than normal Dec-Feb overall. The northeastern Gulf Coast also had a very wet winter, but that was mostly December.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgg7kbhCwkFYZrzX7Wv_DE5Wqgom-u7YPD7gotf7Y0Iq3yNLsS08lIL_nWW_LBrRM9ClWBd4zZOxwExrLkSvXgPwCd1NMWkl4KEkaHQSjwIzAyPACT3iZxgrmV-EGUYkn2O9WtO6QsiFar1v0knIATabt4riBUVEYACvzmeVHf3KszTLd345a6XuNv-lG0/s770/akpcp_2024_DJF.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="770" height="311" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgg7kbhCwkFYZrzX7Wv_DE5Wqgom-u7YPD7gotf7Y0Iq3yNLsS08lIL_nWW_LBrRM9ClWBd4zZOxwExrLkSvXgPwCd1NMWkl4KEkaHQSjwIzAyPACT3iZxgrmV-EGUYkn2O9WtO6QsiFar1v0knIATabt4riBUVEYACvzmeVHf3KszTLd345a6XuNv-lG0/w400-h311/akpcp_2024_DJF.png" width="400" /></a></div><br /><div>As for wind, February was a stormy month for southern (but not Southeast) Alaska, with a big north-south pressure gradient across the Aleutians driving strong winds:</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhUconDTPre6gExDefxoFfxJt3HV-zvnn_V4GY2HqKpDgenIlEJajC8t2dbj_O0-xPVo7m_MRJ51tpAC_b2VfN4IqinxDaR55uo-r7_1DxNNo8AeSzActqjj8EeQbYGErLmlTCAbH39hzr7QrB4_z70y9jAlqerHjArnygNvboPr6QTeOf7C6YO2r5fVhI/s770/akwspd_2024_2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="770" height="311" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhUconDTPre6gExDefxoFfxJt3HV-zvnn_V4GY2HqKpDgenIlEJajC8t2dbj_O0-xPVo7m_MRJ51tpAC_b2VfN4IqinxDaR55uo-r7_1DxNNo8AeSzActqjj8EeQbYGErLmlTCAbH39hzr7QrB4_z70y9jAlqerHjArnygNvboPr6QTeOf7C6YO2r5fVhI/w400-h311/akwspd_2024_2.png" width="400" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjAgLatUOg-EGWVR4cFJUu7_24UasN3fdQtIh8bHMAmmP2xjtcmaLARDtdDJlmQMjovxThyE_0qiv8FBkZ96ChKWsQJYmzmdcEAeQDjVSU1RwrD_-xIAdN0z4zDCyweTJMl_W9CfPXyqZYdpC3nLrzSd1-VA1OD4E0IVeiIJA1p0W_YGaA-q7gN1x_KGXQ/s1027/mslp.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="688" data-original-width="1027" height="268" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjAgLatUOg-EGWVR4cFJUu7_24UasN3fdQtIh8bHMAmmP2xjtcmaLARDtdDJlmQMjovxThyE_0qiv8FBkZ96ChKWsQJYmzmdcEAeQDjVSU1RwrD_-xIAdN0z4zDCyweTJMl_W9CfPXyqZYdpC3nLrzSd1-VA1OD4E0IVeiIJA1p0W_YGaA-q7gN1x_KGXQ/w400-h268/mslp.png" width="400" /></a></div><br /><div>The Dec-Feb wind anomaly pattern is remarkably similar to the February pattern: it was an unusually windy winter from the Aleutians to southwestern and south-central Alaska.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj6bXYltvK8jK51JpV0ssA3a9Rh7pqnfi5PBOXVEQZs1mvy3a6eCkVB_Ka1jbTV56SMgaw-iq4Gp7rgO0RrJqwgMobf2NsRdDqD24zf59JGJE16DpluAFpqra9QzBpxTQd33oPQ1gEWLi-4EGdHT5jM-Jyjv5zwCokJu6BIcHXyyh8iSNhgoU0YXpRRe3Y/s770/akwspd_2024_DJF.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="770" height="311" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj6bXYltvK8jK51JpV0ssA3a9Rh7pqnfi5PBOXVEQZs1mvy3a6eCkVB_Ka1jbTV56SMgaw-iq4Gp7rgO0RrJqwgMobf2NsRdDqD24zf59JGJE16DpluAFpqra9QzBpxTQd33oPQ1gEWLi-4EGdHT5jM-Jyjv5zwCokJu6BIcHXyyh8iSNhgoU0YXpRRe3Y/w400-h311/akwspd_2024_DJF.png" width="400" /></a></div><br /><div>All three aspects of the winter's climate outcome (temperature, precipitation, wind) were quite atypical for a strong El Niño winter. The typical influence of El Niño is to produce unusual warmth in eastern (not western) Alaska, generally below-normal precipitation in most areas, and more often than not reduced winds from the Bering Sea to the northern Gulf.</div><div><br /></div><div>It seems that the main reason for the difference is that El Niño's typical "Aleutian low" was shifted northward into the Bering Sea, and that's likely because there was a strong mid-latitude ridge associated with very unusual oceanic warmth extending east from Japan. The persistence of such widespread warmth in the North Pacific was really unusual for El Niño, which historically has been associated with below-normal wintertime SSTs in the central North Pacific.</div><div><br /></div><div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhK5QwWbMbnP2GquSMlba0j7l3aeaI3oQTjliY9-kG_Yqwc05sQxBtNUN50JMPbCp4ZiACeg5HklRVxXGLGKn64P7aE8DX4SglBrQuqtWTG2JYx-8wGlq5dlYfAzrITLinWr2MN_0VdxcWQfA-wawVcdaVn8OrcEgn9dhFJqCgDzzArKm173xh0VPJ5_cM/s1027/z500.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="688" data-original-width="1027" height="268" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhK5QwWbMbnP2GquSMlba0j7l3aeaI3oQTjliY9-kG_Yqwc05sQxBtNUN50JMPbCp4ZiACeg5HklRVxXGLGKn64P7aE8DX4SglBrQuqtWTG2JYx-8wGlq5dlYfAzrITLinWr2MN_0VdxcWQfA-wawVcdaVn8OrcEgn9dhFJqCgDzzArKm173xh0VPJ5_cM/w400-h268/z500.png" width="400" /></a></div> <div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh1_L7OV-BEPgpoNBO4PrfSG3mF-CNdHFc8yOyasryPPzVqV4a9mgcxskg0R5Ik4wh9V17_ROXf_Yq1XeHQMcIY6NIi2rLUJyNGMgIw9WolFj4VAWCOwm750FcWSqg1-mtzRJy2uc16xBhROni38dIY_5EZPff3F6H8y4Os7PvIuNrTf_y42zhq2_wJO8o/s1027/sst.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="688" data-original-width="1027" height="268" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh1_L7OV-BEPgpoNBO4PrfSG3mF-CNdHFc8yOyasryPPzVqV4a9mgcxskg0R5Ik4wh9V17_ROXf_Yq1XeHQMcIY6NIi2rLUJyNGMgIw9WolFj4VAWCOwm750FcWSqg1-mtzRJy2uc16xBhROni38dIY_5EZPff3F6H8y4Os7PvIuNrTf_y42zhq2_wJO8o/w400-h268/sst.png" width="400" /></a></div><br /></div>Richard Jameshttp://www.blogger.com/profile/08313902028896263276noreply@blogger.com3tag:blogger.com,1999:blog-4572286363399496963.post-26664911684968042942024-03-06T18:32:00.002-09:002024-03-06T18:32:19.649-09:00Yukon at Dawson Still Open<p>This has been a recurring theme in recent years, and a problem for residents of Dawson, YT: the Yukon River is reluctant to freeze over next to town. As in some other recent winters, it hasn't been possible to build the usual ice bridge across to West Dawson. Here's today's webcam view, suggesting that a complete freeze-up won't occur at all this winter:</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiPWDiHOEy4JPJ6okUQIvvPxrW-zI-6z_aeOhda2K3GwEA-I2q0q3GIj0kSSlJEN3IuQZAw2Vby-35Phzt5E4ad000xd4YW8d0UpDj0q0VxjXhXhGTe8BxY6o00UM5ABNc2GG3qEU-71Re5pSnhmhvV_Y6x9jNuDZffEb-5_e35SMOFpI-ZzSJRK13tyI8/s1280/dawson_20240306.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="1280" height="250" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiPWDiHOEy4JPJ6okUQIvvPxrW-zI-6z_aeOhda2K3GwEA-I2q0q3GIj0kSSlJEN3IuQZAw2Vby-35Phzt5E4ad000xd4YW8d0UpDj0q0VxjXhXhGTe8BxY6o00UM5ABNc2GG3qEU-71Re5pSnhmhvV_Y6x9jNuDZffEb-5_e35SMOFpI-ZzSJRK13tyI8/w400-h250/dawson_20240306.jpg" width="400" /></a></div><br /><p>And a video confirming the flow of water in the open channel:</p><div class="separator" style="clear: both; text-align: center;"><iframe allowfullscreen='allowfullscreen' webkitallowfullscreen='webkitallowfullscreen' mozallowfullscreen='mozallowfullscreen' width='320' height='266' src='https://www.blogger.com/video.g?token=AD6v5dzFsxiQ6lULZsE_1wGME1yEM40KHZLEyDe6oGaCeJiT3R5gYaZcAGDpQD881eT7ZKiJXl_ffk6WBJmmMWQA7A' class='b-hbp-video b-uploaded' frameborder='0'></iframe></div><br /><p>November and December were significantly warmer than normal in Dawson, but January and February were both slightly colder than normal, so it seems unlikely that the lack of ice can be blamed on the weather.</p>Richard Jameshttp://www.blogger.com/profile/08313902028896263276noreply@blogger.com5tag:blogger.com,1999:blog-4572286363399496963.post-17495559545909584642024-03-04T18:09:00.005-09:002024-03-04T18:09:59.233-09:00Anchorage Wind<p>A reader inquired about the persistent north wind event of last week in the Anchorage area, so let's take a look at this.</p><p>First, the facts on the ground: there was indeed a very lengthy period of stiff northerly winds, lasting from early morning on Wednesday (Feb 28) through Saturday morning (March 2). Here's a graphical look at observations from Anchorage airport, with wind speeds in mph:</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhpPZFFr5aBxRAJnH-xs3LuqUO0l-pstuq94rvJLkymVpiQg_NnuRm4m1dPOwmjHyZJ3ZieGNR4EhHPAgRotDyoEnQ_GI6ZPIFX14OtYFPa5LPlawlJRoNKy-v8HbP_vTCkgrgGA43tIbuS9rzkvdwjBnoyBLzeF4y4VF-JcwP_q2c9Ibch8_WnIoYY96k/s1170/wind_panc.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="581" data-original-width="1170" height="199" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhpPZFFr5aBxRAJnH-xs3LuqUO0l-pstuq94rvJLkymVpiQg_NnuRm4m1dPOwmjHyZJ3ZieGNR4EhHPAgRotDyoEnQ_GI6ZPIFX14OtYFPa5LPlawlJRoNKy-v8HbP_vTCkgrgGA43tIbuS9rzkvdwjBnoyBLzeF4y4VF-JcwP_q2c9Ibch8_WnIoYY96k/w400-h199/wind_panc.png" width="400" /></a></div><br /><p>Much the same sort of thing was observed up in Palmer, and with higher wind speeds, although there was a break on Thursday morning:</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjHyn6kOjPGZMHSmy5UQfRJO66GF-BHY8-52vZpMtvJvjLxEe3EF9zMUEGGdEfTAMOqQ3MfpsaqW4O4YCUjRkGrjfBOXfG7Vxd6momHl2oLeMC1eCF4gyhdwuwDYyA8DM1PbG-Nm8SiPlaWByU2-LdrlYJJRHoaLUPlLTZL2FziQNU_zZGKh0ycRBZ6Jg0/s1177/wind_paaq.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="589" data-original-width="1177" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjHyn6kOjPGZMHSmy5UQfRJO66GF-BHY8-52vZpMtvJvjLxEe3EF9zMUEGGdEfTAMOqQ3MfpsaqW4O4YCUjRkGrjfBOXfG7Vxd6momHl2oLeMC1eCF4gyhdwuwDYyA8DM1PbG-Nm8SiPlaWByU2-LdrlYJJRHoaLUPlLTZL2FziQNU_zZGKh0ycRBZ6Jg0/w400-h200/wind_paaq.png" width="400" /></a></div><br /><p>Remarkably, the peak wind gusts were 60mph or higher for 4 consecutive days in Palmer. The maps below (click to enlarge) show the daily peak gusts from Feb 28 (top) to March 2 (bottom). This was a remarkably persistent event:</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEib-GXWjo4neJfu9v8U-AnGwh6_P7f21ILatNWNoKpUss09fVOeZs5u__ATXc36QQvprWhWzhqqdcGnpoiOBYhaQIc_NFmx8PncKi4BaQQpA9bz6Ta3SPXDt7YjI8jYVyYUAaN9KfVNNv1Z2Wav75sYlx45KwwUf2hL1UG6c_pQqC6V8H5Nx02aHXjWV-c/s999/wind_panc_20240228.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="816" data-original-width="999" height="326" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEib-GXWjo4neJfu9v8U-AnGwh6_P7f21ILatNWNoKpUss09fVOeZs5u__ATXc36QQvprWhWzhqqdcGnpoiOBYhaQIc_NFmx8PncKi4BaQQpA9bz6Ta3SPXDt7YjI8jYVyYUAaN9KfVNNv1Z2Wav75sYlx45KwwUf2hL1UG6c_pQqC6V8H5Nx02aHXjWV-c/w400-h326/wind_panc_20240228.jpg" width="400" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7cZu-wMcVLWTpMsQMfdtovNPDX7EBXRNcYMi28ewd75EDIg5Ddz-ZecJbQ9L3HGU_DDP_Vu6260cNFDlph6W3UBFsuQoybw3Xzv4jM_qKHCNISYe6MiYu8iZ51fklc6Q3NHLsBcvU-5tlIucaTqTup1PZ9Nci_UW04wu3NHk-JuEDwUJ9tE28Kh8Fhwk/s999/wind_panc_20240229.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="816" data-original-width="999" height="326" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7cZu-wMcVLWTpMsQMfdtovNPDX7EBXRNcYMi28ewd75EDIg5Ddz-ZecJbQ9L3HGU_DDP_Vu6260cNFDlph6W3UBFsuQoybw3Xzv4jM_qKHCNISYe6MiYu8iZ51fklc6Q3NHLsBcvU-5tlIucaTqTup1PZ9Nci_UW04wu3NHk-JuEDwUJ9tE28Kh8Fhwk/w400-h326/wind_panc_20240229.jpg" width="400" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh8G2DgpV29fODo2TRs7-Mbr07PI5TCkbj57Uu7gjyCmhqR_7l8TbstZb8Rf0pYfd_Eb6kfRcpNXb2oY-iqAt-Koi8HgoOxJUiCAhU4gYIC5sC9C_AMAq4Rox18AMtm5Zw4Dg_iEBNMVU35pAo1jzIsOfRMWhrlMhIKwqpmVIaJU-5WLxb6Fzsa-Sryb4Y/s999/wind_panc_20240301.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="816" data-original-width="999" height="326" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh8G2DgpV29fODo2TRs7-Mbr07PI5TCkbj57Uu7gjyCmhqR_7l8TbstZb8Rf0pYfd_Eb6kfRcpNXb2oY-iqAt-Koi8HgoOxJUiCAhU4gYIC5sC9C_AMAq4Rox18AMtm5Zw4Dg_iEBNMVU35pAo1jzIsOfRMWhrlMhIKwqpmVIaJU-5WLxb6Fzsa-Sryb4Y/w400-h326/wind_panc_20240301.jpg" width="400" /></a></div><div class="separator" style="clear: both; text-align: center;"><br /><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi7GyncCUuO1ephehuT4UpmwHXw7xmwTCGicHUm2Kdep-3kHrViUizASIrfMEtR-E0W5L4vmkWMt0SpQ1P85_Fklz1lXVpxw4ADVALfHpNMMeEPXSEYCYz6qjdDTJOIXeNYzuAqid7bRTZt3AtN5-Yo8ai0Fu50T5CPBySocRCLQ6WPD7mqEhYCclerEBY/s999/wind_panc_20240302.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="816" data-original-width="999" height="326" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi7GyncCUuO1ephehuT4UpmwHXw7xmwTCGicHUm2Kdep-3kHrViUizASIrfMEtR-E0W5L4vmkWMt0SpQ1P85_Fklz1lXVpxw4ADVALfHpNMMeEPXSEYCYz6qjdDTJOIXeNYzuAqid7bRTZt3AtN5-Yo8ai0Fu50T5CPBySocRCLQ6WPD7mqEhYCclerEBY/w400-h326/wind_panc_20240302.jpg" width="400" /></a></div><p><br /></p><p>Taking a quick look at historical hourly data from Anchorage airport, I see only one other event since 2000 with comparable sustained winds: it looks like a very similar event occurred at the same point on the calendar in 2017 (Feb 28 - March 3). Here's the average MSLP for the 3 windiest days in both cases: 2017 (top) and 2024 (bottom):</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgg_MzC6DuvKqaJcayRQG-wdsXMFb6lDDV6n_NqzxiXd0tmXOFJwPL6qIBfoYMzs_V9vvKHGHQ8KoDI6ZGhCqFRD3ofRwH0jJmQLYfbaHwFYp35DpNDsc8Ov_jDj8fHlwicbxrz1xhlWfJvOCJwfPSWfU60GXsKPxl8B0nHre0uYHqRFTA0sUWG6gZSqVY/s1050/compday.1kgDIww37x.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="813" data-original-width="1050" height="310" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgg_MzC6DuvKqaJcayRQG-wdsXMFb6lDDV6n_NqzxiXd0tmXOFJwPL6qIBfoYMzs_V9vvKHGHQ8KoDI6ZGhCqFRD3ofRwH0jJmQLYfbaHwFYp35DpNDsc8Ov_jDj8fHlwicbxrz1xhlWfJvOCJwfPSWfU60GXsKPxl8B0nHre0uYHqRFTA0sUWG6gZSqVY/w400-h310/compday.1kgDIww37x.gif" width="400" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi9vURmN5EYLZssqFvfySdXIj3QJ5AXMHeMOm3Xmipw7nh3f6kbFccT2tJ3QTGkBm8ZzuaEWKjZLOY2TFUbH1j08WUnCyKVpRBjDMaVbgJbGBRYpiALp1vpuC2IHVTiT_fw-RhkHGHLYZdVBLTgkY0_4MB1fLZNd9QQvanekVcTvM5PLH-bcK13m3Cyjm8/s1050/compday.zWIKUKLdRS.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="813" data-original-width="1050" height="310" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi9vURmN5EYLZssqFvfySdXIj3QJ5AXMHeMOm3Xmipw7nh3f6kbFccT2tJ3QTGkBm8ZzuaEWKjZLOY2TFUbH1j08WUnCyKVpRBjDMaVbgJbGBRYpiALp1vpuC2IHVTiT_fw-RhkHGHLYZdVBLTgkY0_4MB1fLZNd9QQvanekVcTvM5PLH-bcK13m3Cyjm8/w400-h310/compday.zWIKUKLdRS.gif" width="400" /></a></div><br /><p>Clearly the driving factor in both cases was the strong pressure gradient between low pressure in the eastern Gulf of Alaska and high pressure to the west and north.</p><p>The long duration of the event reflects the unusually persistent MSLP setup, with low pressure slow to depart or weaken in the Gulf of Alaska, and with building high pressure to the north maintaining the gradient as the low pressure eventually decayed. Here's a sequence of MSLP analyses at 3am AKST for 5 consecutive days: February 27 through March 2.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjRcNx0gladbt1w1c6b_OqTQg-BOPwAAZhP-fHUyzfByT-CZpaTK5a27JQVcnm32yY0515AZbGWHpzqRumER3rXkDHZR8kVBZZL6eDN1oM2t9Xgz2Cxpfozx5Z03AjCGS8zBWsOxYavOF5KCBs9n_3mJFjYfZfCjd9eXtItlAzY67SLESdrg5Al7Aw_96s/s989/mslp.2.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="730" data-original-width="989" height="295" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjRcNx0gladbt1w1c6b_OqTQg-BOPwAAZhP-fHUyzfByT-CZpaTK5a27JQVcnm32yY0515AZbGWHpzqRumER3rXkDHZR8kVBZZL6eDN1oM2t9Xgz2Cxpfozx5Z03AjCGS8zBWsOxYavOF5KCBs9n_3mJFjYfZfCjd9eXtItlAzY67SLESdrg5Al7Aw_96s/w400-h295/mslp.2.png" width="400" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgRu_vHHSld7YHdAt1Pj9wI9LkEeMV8hRfY675_KZfa3YJeiMNRfylvIx8VFIh4sfzJfduVVODdAZ2nBjMrif5ixYHFx4YggZv2_vWuMrw5MfNceh6d9Y-SHJIN8w1WDW1aM42BteWPnAoyS5ImJoWW429zTSmf0r4X7wea0lCvt2xS60X9fJIzZip_yyY/s989/mslp.3.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="730" data-original-width="989" height="295" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgRu_vHHSld7YHdAt1Pj9wI9LkEeMV8hRfY675_KZfa3YJeiMNRfylvIx8VFIh4sfzJfduVVODdAZ2nBjMrif5ixYHFx4YggZv2_vWuMrw5MfNceh6d9Y-SHJIN8w1WDW1aM42BteWPnAoyS5ImJoWW429zTSmf0r4X7wea0lCvt2xS60X9fJIzZip_yyY/w400-h295/mslp.3.png" width="400" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgegahMozz7xg43AIW17yp77IrPdkrVa3b9cLOchGLc5xJOM33E7gWboK47cgwA7gTDkWdnXqHDqIkLEPxk70xwz9C07MKtWr9b2qZQe7KR0gCKJGHac8gtGkMh53fHJQUUSR1H7quNi82VxFCsrIQj1QgO0OykIGWVrj7WqvuOnXrH5peUkl_sZt5Ivk0/s989/mslp.4.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="730" data-original-width="989" height="295" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgegahMozz7xg43AIW17yp77IrPdkrVa3b9cLOchGLc5xJOM33E7gWboK47cgwA7gTDkWdnXqHDqIkLEPxk70xwz9C07MKtWr9b2qZQe7KR0gCKJGHac8gtGkMh53fHJQUUSR1H7quNi82VxFCsrIQj1QgO0OykIGWVrj7WqvuOnXrH5peUkl_sZt5Ivk0/w400-h295/mslp.4.png" width="400" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhOubByVKjOltWkjw5Y4JhOo7motg5vyiIGH_6GmqBSihLoiQ-6KKAkDvsNO6Y58BQO1mLPDZLgJrn85YZMt6lRMX9_esENMs-sEjm_-NIDo3nNy8h9Uhs-jh7UGmjVbHFL2MPIqzBQW1XDOUUxzZETa5fkLZLlNNCt4g-dx4vhiyVhQuDi8zwCsgYIWqc/s989/mslp.5.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="730" data-original-width="989" height="295" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhOubByVKjOltWkjw5Y4JhOo7motg5vyiIGH_6GmqBSihLoiQ-6KKAkDvsNO6Y58BQO1mLPDZLgJrn85YZMt6lRMX9_esENMs-sEjm_-NIDo3nNy8h9Uhs-jh7UGmjVbHFL2MPIqzBQW1XDOUUxzZETa5fkLZLlNNCt4g-dx4vhiyVhQuDi8zwCsgYIWqc/w400-h295/mslp.5.png" width="400" /></a></div><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><br /></div><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiQQIMLU0u3eEIOyCygU9uu846tdnaWxH88tI5biw7Y8K0NMd-dVJj0SZnwpYab_Gbcg9lYF19JLUUTpiQC-5OiuMHvrXzNrXJI_8xDL1frwZ2pSlylipQE0WSRumYxcJH-ybc_sGlW5HWd4QnGuDg1sgCIF2n_FM7KIBPJFsO7Vcg1MnRFXTsF1TbCIB4/s989/mslp.6.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="730" data-original-width="989" height="295" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiQQIMLU0u3eEIOyCygU9uu846tdnaWxH88tI5biw7Y8K0NMd-dVJj0SZnwpYab_Gbcg9lYF19JLUUTpiQC-5OiuMHvrXzNrXJI_8xDL1frwZ2pSlylipQE0WSRumYxcJH-ybc_sGlW5HWd4QnGuDg1sgCIF2n_FM7KIBPJFsO7Vcg1MnRFXTsF1TbCIB4/w400-h295/mslp.6.png" width="400" /></a></div><br /><p>Farther aloft, the situation was unusual, with a sharp ridge over the Bering Sea progressing slowly eastward behind a broad and deep trough over the Gulf of Alaska. The 500mb map from Thursday afternoon shows powerful northwesterly flow in the very tight pressure gradient over southwestern Alaska, but yet the 500mb wind was out of the south at Anchorage (highlighted with the red circle below):</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEimeMl1LOCwkeImXWix7E3lKovvYobk8lSFVqBlhbRl7IBwEIQI8CnTUJNqh5_81NSAMPUeDHOA3fPuV-72-z6IvsASdoUecc_1PN1XH4BkVINvklEfdwj3GRa-AT8BaYYY_jmLP7ncONCcivTt6Sg6oJPHzf7GySwPxfkdAVeKPEF23hV6rdq30VNPMnM/s1159/z500.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="877" data-original-width="1159" height="303" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEimeMl1LOCwkeImXWix7E3lKovvYobk8lSFVqBlhbRl7IBwEIQI8CnTUJNqh5_81NSAMPUeDHOA3fPuV-72-z6IvsASdoUecc_1PN1XH4BkVINvklEfdwj3GRa-AT8BaYYY_jmLP7ncONCcivTt6Sg6oJPHzf7GySwPxfkdAVeKPEF23hV6rdq30VNPMnM/w400-h303/z500.png" width="400" /></a></div><br /><p>To me, this highlights the large degree of spin (technically "vorticity") in the atmosphere aloft, which helps explain the longevity of the low pressure in the northeastern Gulf of Alaska. This upper trough and associated jet stream, by the way, is what brought extreme mountain snows to California over the weekend. It was windy down there too: there's a lot of energy in this jet stream, and this is probably attributable to El Niño.</p>Richard Jameshttp://www.blogger.com/profile/08313902028896263276noreply@blogger.com1tag:blogger.com,1999:blog-4572286363399496963.post-44943935015939231182024-03-01T18:19:00.003-09:002024-03-01T18:19:41.093-09:00ECMWF AI ForecastsThe weather industry has been abuzz with excitement in the past year about the new AI (Artificial Intelligence) forecast models; I penned a few comments back in November:<div><br /></div><div><a href="https://ak-wx.blogspot.com/2023/11/ai-weather-forecasts.html">https://ak-wx.blogspot.com/2023/11/ai-weather-forecasts.html</a></div><div><br /></div><div>The latest news is that ECMWF is now providing the realtime forecast data from its AIFS model, and it's open and free for all to use. You can see the 4 forecasts per day on Levi Cowan's website:<br /><br /></div><div><a href="https://www.tropicaltidbits.com/analysis/models/?model=ec-aifs&region=ak&pkg=mslp_pcpn">https://www.tropicaltidbits.com/analysis/models/?model=ec-aifs&region=ak&pkg=mslp_pcpn</a></div><div><br /></div><div>The skill of the model is comparable to the leading physics-based models, so the new data will provide a useful tool for forecasters. I'll be keeping an eye on it for Alaska.</div><div><br /></div><div>We should bear in mind, however, that ECMWF currently runs only a single AIFS forecast each time, rather than an ensemble of forecasts like the ECMWF, NOAA, and Canadian ensemble systems. Ensemble forecasts provide valuable information on confidence ("how similar are the ensemble members?"), and the ensemble-average forecasts tend to be more stable from run to run. The AIFS forecasts will have a tendency to jump around from run to run, so take each iteration with a pinch of salt.</div><div><br /></div><div>For example, here are the 4 latest AIFS forecasts for the morning of March 11, i.e. 10 days ahead, and probably at or beyond the limit of deterministic predictability for the Alaska region. From oldest to newest forecasts:</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiw_19B6cB7ZvkjUjXV_oKXuHakXpVaCOcHJGf01CTR1h5G6Y43DdRIufVufa0zRSMDR2lbdwDiJa8sOIq3De_pJ3kXrL_uOn_qUEjG783hMOavxekyVBhHNx0ljGykLRL34qdo3L9oNcoB84o4nNK-IKuHc7jLuw5KEPVydBNx35TfxovkV-mKxzMegK0/s1024/ec-aifs_T850a_ak_44.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="809" data-original-width="1024" height="316" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiw_19B6cB7ZvkjUjXV_oKXuHakXpVaCOcHJGf01CTR1h5G6Y43DdRIufVufa0zRSMDR2lbdwDiJa8sOIq3De_pJ3kXrL_uOn_qUEjG783hMOavxekyVBhHNx0ljGykLRL34qdo3L9oNcoB84o4nNK-IKuHc7jLuw5KEPVydBNx35TfxovkV-mKxzMegK0/w400-h316/ec-aifs_T850a_ak_44.png" width="400" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhZdH7zaJJMI4cWrx8PBw_acBF-1yrJbolko7-lkoSZNOg6rcuy1L8lmhyphenhyphenK5lNREJpY7zRFUCveELHrQIdv9jyM1fYq36YbCU7gAboIlDn1KRLa9oatDWtWTvTsRgKv_bfdtEzyZMjAxJJk73caMIYyTDq_uobGeVXEXV8Li3ErPEogrn-AzWsjpNIDHSQ/s1024/ec-aifs_T850a_ak_43.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="809" data-original-width="1024" height="316" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhZdH7zaJJMI4cWrx8PBw_acBF-1yrJbolko7-lkoSZNOg6rcuy1L8lmhyphenhyphenK5lNREJpY7zRFUCveELHrQIdv9jyM1fYq36YbCU7gAboIlDn1KRLa9oatDWtWTvTsRgKv_bfdtEzyZMjAxJJk73caMIYyTDq_uobGeVXEXV8Li3ErPEogrn-AzWsjpNIDHSQ/w400-h316/ec-aifs_T850a_ak_43.png" width="400" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEheCXBave4uNwhFy3WaMJKibfH6zJfcXDkvxgFKY5vk04gqflycy9v6P-26gZgybkI1ugYogj6rsMKBSlInF0nbqCJR2ErndN12tH_I6NsSLAze-3w_gQUo93LtdHYxiIlj8aQQsn7YkTkWQgRzSeKFL4gacFPPLmtIQUl8piLSL0_DkFeGtNgH-GYyBlU/s1024/ec-aifs_T850a_ak_42.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="809" data-original-width="1024" height="316" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEheCXBave4uNwhFy3WaMJKibfH6zJfcXDkvxgFKY5vk04gqflycy9v6P-26gZgybkI1ugYogj6rsMKBSlInF0nbqCJR2ErndN12tH_I6NsSLAze-3w_gQUo93LtdHYxiIlj8aQQsn7YkTkWQgRzSeKFL4gacFPPLmtIQUl8piLSL0_DkFeGtNgH-GYyBlU/w400-h316/ec-aifs_T850a_ak_42.png" width="400" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjppSHA5IV9enHjvthKWTbxHI118MgNjNtKYBmBs04zKveC2kOux8PsneYZkgiChL0jfOdSaIeKUe3gekFnV41Tdk5hUnSuQ_LcayUf3AqScxfTjo0saI5PlaAlACtaf1Qj8sY0LLcFSZR1457Aeev0jMqcLcmRTtAig-lTlIZ8T9zjyF4vYVLpPtIFl5c/s1024/ec-aifs_T850a_ak_41.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="809" data-original-width="1024" height="316" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjppSHA5IV9enHjvthKWTbxHI118MgNjNtKYBmBs04zKveC2kOux8PsneYZkgiChL0jfOdSaIeKUe3gekFnV41Tdk5hUnSuQ_LcayUf3AqScxfTjo0saI5PlaAlACtaf1Qj8sY0LLcFSZR1457Aeev0jMqcLcmRTtAig-lTlIZ8T9zjyF4vYVLpPtIFl5c/w400-h316/ec-aifs_T850a_ak_41.png" width="400" /></a></div><br /><div>The general theme is the same - cold in northern Alaska - but the individual forecasts disagree on the extent of cold farther south.</div><div><br /></div><div>For comparison, here's the NOAA GEFS ensemble mean for the same time. In this case the overall agreement is pretty good; and these forecasts (GEFS vs AIFS) are produced by completely different methods. Impressive technology for sure!</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhaxpHvbK43RNTsaAdBL2ols5u2EEmOn0yuO7BiH-IrLujk63EdYWlt5WLFHnyM66M8YnxuDyKvloAGW3hZZPIgvI3-rhTLbLrHMjtuF6anuWhDzu-u2SV9hqrnGPP43WqXr76137A89kokIbwwqJklvrbcsve_dDCb5zdz6Pc4wGmzZMg816ooMt9QXx0/s1024/gfs-ens_T850a_ak_41.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="809" data-original-width="1024" height="316" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhaxpHvbK43RNTsaAdBL2ols5u2EEmOn0yuO7BiH-IrLujk63EdYWlt5WLFHnyM66M8YnxuDyKvloAGW3hZZPIgvI3-rhTLbLrHMjtuF6anuWhDzu-u2SV9hqrnGPP43WqXr76137A89kokIbwwqJklvrbcsve_dDCb5zdz6Pc4wGmzZMg816ooMt9QXx0/w400-h316/gfs-ens_T850a_ak_41.png" width="400" /></a></div><br /><div><br /></div>Richard Jameshttp://www.blogger.com/profile/08313902028896263276noreply@blogger.com3tag:blogger.com,1999:blog-4572286363399496963.post-69019299133635942782024-02-28T17:27:00.002-09:002024-02-28T17:27:26.589-09:00Calendar of Cold<p>It's back to cold(er than normal) in Alaska again, with a brisk -31°F observed at Fairbanks airport this morning, and -40°F in colder spots to the north, including Bettles. Wind chills are unpleasant on the North Slope too, but as noted by reader Mike, Arctic Alaska is very much still locked in winter. The seasonal minimum in temperature occurs a lot later for the North Slope - and indeed for many of Alaska's coastal locations - than for the interior.</p><p>For a visual perspective on the timing of the seasonal minimum, here's a map based on ERA5 1991-2020 data.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgwAIToAgTeQJ48oUegsTy8HcTkNC_uVkAaePx3h4DXS-hkCXKk51IkRrA7uBGwEqjDzoxeAL_9aa82r388UoWDI6rWqnr-T4fAyKU2jLGhIsT6BP6JnLuBVw_UaYzuJv3DhjWOjLHWbrsY68Gzv5WvOSDknhPaUvjIfemGdftABScb9MfzELOfSE51xDo/s985/climo_t2m_min_date_ak.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="750" data-original-width="985" height="305" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgwAIToAgTeQJ48oUegsTy8HcTkNC_uVkAaePx3h4DXS-hkCXKk51IkRrA7uBGwEqjDzoxeAL_9aa82r388UoWDI6rWqnr-T4fAyKU2jLGhIsT6BP6JnLuBVw_UaYzuJv3DhjWOjLHWbrsY68Gzv5WvOSDknhPaUvjIfemGdftABScb9MfzELOfSE51xDo/w400-h305/climo_t2m_min_date_ak.png" width="400" /></a></div><p>According to this analysis, the seasonal temperature cycle bottoms out before the turn of the year for a few areas in western and interior Alaska, but most of the interior sees its coldest "normals" in the first half of January. Cold peaks later for the North Slope - the first half of February for the eastern North Slope - and the highly maritime climate of the North Pacific sees a seasonal minimum even later, in late February or even early March. The pronounced lag over the ice-free Pacific is related to the very large heat capacity of the ocean's upper layers, as well as the ample cloud cover that prevents a strengthening sun from bringing warmth to the ocean surface.</p><p>I'm a little surprised by the early seasonal minimum for coastal western Alaska, where I would have expected sea ice to keep temperatures suppressed to a later date. The ERA5 results are confirmed by the NCEI 1991-2020 daily normals: Nome has its lowest normal temperature around January 12, and Bethel around January 9. For comparison, Fairbanks also bottoms out around January 12. I don't know why the west coast doesn't have more of a maritime influence in this aspect of the climate.</p><p>But a couple of caveats are worth noting in this analysis. First, I'm using harmonic functions to smooth the seasonal temperature cycle through the year, and the details of the method (e.g. the number of functions) can affect the timing of the estimated seasonal minimum. Second, the sample size of 30 years also implies some uncertainty in the date of the minimum, because the random timing of major historical cold and warm episodes will affect the details of the calculated cycle. It would be interesting to quantify the uncertainty with some statistical experiments.</p><p>On a broader scale, the map below shows that the European side of the Arctic Ocean has a later seasonal minimum than the Pacific side: it even extends past March 15 for a small area near Iceland.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgJHx9cpKX-hNn2BxapX4Z0bA7hh4seNuKva5ff1-mpTND7WkFDedP7RAn_Frw3J6OMza2GKZWKHS9M7uIpfG9HQnvuzj_O_1chmiZBclKj8mMHYFuOH49HjoAKf9fNzYOHd9GbrSvxi8MNXtnOae5GFjGO9SgHzzgPSOjnuWZZCQgVOR-F66r1sW_b7Pk/s942/climo_t2m_min_date_nhem.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="750" data-original-width="942" height="319" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgJHx9cpKX-hNn2BxapX4Z0bA7hh4seNuKva5ff1-mpTND7WkFDedP7RAn_Frw3J6OMza2GKZWKHS9M7uIpfG9HQnvuzj_O_1chmiZBclKj8mMHYFuOH49HjoAKf9fNzYOHd9GbrSvxi8MNXtnOae5GFjGO9SgHzzgPSOjnuWZZCQgVOR-F66r1sW_b7Pk/w400-h319/climo_t2m_min_date_nhem.png" width="400" /></a></div><br /><p>And expanding the domain into the mid-latitudes, we see that the eastern North Pacific has the latest seasonal minimum of anywhere in the hemisphere: as late as March 29 according to this analysis.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg6a2QyxgKbUZJWlBkgDaA8uo7EpHBK0SSl93SJoN5bxFGatYfKeAyVnvVQZLrFFvwKQEwQRW9nYto_neN_MoGnoBJ2ijOuYNiIwQ85l11YAxPCg2gz596lYZXTlppg4aJKzDW6auKrGNuxx2aKZFAcdcxTE0mIIB87O0W6j7FBPigg6ZXrGPsOu59cpuQ/s942/climo_t2m_min_date_nhem1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="750" data-original-width="942" height="319" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg6a2QyxgKbUZJWlBkgDaA8uo7EpHBK0SSl93SJoN5bxFGatYfKeAyVnvVQZLrFFvwKQEwQRW9nYto_neN_MoGnoBJ2ijOuYNiIwQ85l11YAxPCg2gz596lYZXTlppg4aJKzDW6auKrGNuxx2aKZFAcdcxTE0mIIB87O0W6j7FBPigg6ZXrGPsOu59cpuQ/w400-h319/climo_t2m_min_date_nhem1.png" width="400" /></a></div><br /><p>Another question I can't answer is why the eastern North Pacific has so much more lag than the western North Pacific. Perhaps it's as simple as the western ocean being influenced by continental air from the vast land mass of Asia, which warms up quickly in late winter.</p><p><br /></p>Richard Jameshttp://www.blogger.com/profile/08313902028896263276noreply@blogger.com6tag:blogger.com,1999:blog-4572286363399496963.post-63877193398312159102024-02-21T18:03:00.002-09:002024-02-21T18:03:45.382-09:00More Context for Cold<p>Another round of downslope/chinook warming brought another widespread thaw to the Tanana River valley and Fairbanks-land yesterday. Temperatures above 40°F were widespread, including 45°F at Fairbanks airport, the highest February temperature in 20 years. The year-to-date average temperature in Fairbanks is now only 2.2°F below normal.</p><p>Looking back again at the late January and early February cold snap, I was curious to see how the lower atmosphere (not surface) temperatures compared to past cold spells on various time scales. However, with NWS weather balloons no longer going up during severe cold, there's some missing data for the recent event; so I extracted data from the ERA5 reanalysis. I looked at Fairbanks 850mb temperatures and 1000-500mb thickness, with the latter being an excellent measure of the average temperature of the lower half of the atmosphere.</p><p>Here's the annual (winter) minimum for 3-day average 1000-500mb thickness:</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgpZfOp4HlG907ZKA4WesCTYw2NqjeJIf4spC9_wsHB9w_5lowyapLf9Su2fHhgw8E4GJChcKcpVIeDvoJ5ME4ZTBblUttxNUemObyuPYzqBV5ShzJ-7zh8OKH_1lDqz8K_IGnncE8ttjhfeAp_v14whDhTH7ua6QUAOPEcmmGkZYRkIoS4iKptN9LtDdo/s1981/pafa_cold_thk500_3day.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1239" data-original-width="1981" height="250" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgpZfOp4HlG907ZKA4WesCTYw2NqjeJIf4spC9_wsHB9w_5lowyapLf9Su2fHhgw8E4GJChcKcpVIeDvoJ5ME4ZTBblUttxNUemObyuPYzqBV5ShzJ-7zh8OKH_1lDqz8K_IGnncE8ttjhfeAp_v14whDhTH7ua6QUAOPEcmmGkZYRkIoS4iKptN9LtDdo/w400-h250/pafa_cold_thk500_3day.png" width="400" /></a></div><br /><p>On this time scale, the recent event was one of the coldest since 2000, but it was nowhere near as cold as the more extreme events of earlier decades. The complete absence of seriously cold events after 2000 is quite remarkable, and suggests that the cold tail of the distribution has been dramatically curtailed since then.</p><p>Below is another perspective, showing annual minimum values of 3-day 850mb temperature (y-axis) versus 1000-500mb thickness (x-axis). The values are quite highly correlated, of course, but there's some variability in the extent to which cold is concentrated at lower atmosphere levels like 850mb. On a 3-day basis, the recent event was relatively less unusual in terms of 850mb temperature, with several other events being colder in recent years.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUSwpzF_KoyaTwb3WXl03TichGgpufFqJECLBZolaDDHeWap3WfBwTw1cbGKnEjal3QAoHJcAIfD57hIaAuA9hHoqgd4vjsfYnwxcHJuBCOUw-nEXqgZG7iTqVrkVPU-v56doNj-uloYaalAD99Vo20mdT9Ga7t5rqH2xmC3-qcHSXCQdSHR20r8g7nV8/s1951/pafa_cold_thk500_t850_3day.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1225" data-original-width="1951" height="251" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUSwpzF_KoyaTwb3WXl03TichGgpufFqJECLBZolaDDHeWap3WfBwTw1cbGKnEjal3QAoHJcAIfD57hIaAuA9hHoqgd4vjsfYnwxcHJuBCOUw-nEXqgZG7iTqVrkVPU-v56doNj-uloYaalAD99Vo20mdT9Ga7t5rqH2xmC3-qcHSXCQdSHR20r8g7nV8/w400-h251/pafa_cold_thk500_t850_3day.png" width="400" /></a></div><br /><p>The 7-day and 14-day charts below show quite similar findings on these time scales, with the recent event being a bit more anomalous overall on a 14-day basis, as I <a href="https://ak-wx.blogspot.com/2024/02/cold-in-context.html">noted before</a>; but it was still not in the least unusual compared to earlier decades.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhfX0rdGl1GipiTFNkhNdMQHfFVGeeMxKF9r0Pvjxvfy-6qeWYppdS3-6C7PUsOCgkIck2bPwPUErkQwk00gvO6dxHP1v0SPR_t1Puyr8ANH-uyjTr8AKX7jKDXCNPKuafB3Cjp3nAXkBvlT0bHBxd_5_d-e1nhAYNI-gD21Lb4_2Pp3_xaxmvPqHcxvhg/s1949/pafa_cold_thk500_t850_7day.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1227" data-original-width="1949" height="251" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhfX0rdGl1GipiTFNkhNdMQHfFVGeeMxKF9r0Pvjxvfy-6qeWYppdS3-6C7PUsOCgkIck2bPwPUErkQwk00gvO6dxHP1v0SPR_t1Puyr8ANH-uyjTr8AKX7jKDXCNPKuafB3Cjp3nAXkBvlT0bHBxd_5_d-e1nhAYNI-gD21Lb4_2Pp3_xaxmvPqHcxvhg/w400-h251/pafa_cold_thk500_t850_7day.png" width="400" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjV0_GC9Gwaq-Q57HtFp79-XuZWwMJSeOJ7abtULOKQICFwSRS9gIpEPgUUePjlTO0d50zNdjvQjszH_M6Y82NFjaxTkcL2sVR8HtzuvL4Z65GO0ZnFcN1JhK7ZFzzV7gJY3UeT1KmYWZpDPqhTGjNEKgMHN2JjQr94uYK2VaVIqG8FdXFz-K_GBACiRvE/s1954/pafa_cold_thk500_t850_14day.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1234" data-original-width="1954" height="253" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjV0_GC9Gwaq-Q57HtFp79-XuZWwMJSeOJ7abtULOKQICFwSRS9gIpEPgUUePjlTO0d50zNdjvQjszH_M6Y82NFjaxTkcL2sVR8HtzuvL4Z65GO0ZnFcN1JhK7ZFzzV7gJY3UeT1KmYWZpDPqhTGjNEKgMHN2JjQr94uYK2VaVIqG8FdXFz-K_GBACiRvE/w400-h253/pafa_cold_thk500_t850_14day.png" width="400" /></a></div><br /><p>The two "granddaddy" cold spells of 1989 and 1999 stand out clearly here; those two events were much more extreme than anything in recent years, and also worse than anything that happened in the otherwise colder 1950s, 60s, and 70s.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEghBWvXqmPZQ628qS8ALrdRLAYCLYp6OjalI90giNz20RvIWZWMtRZKPkpNw82jh0AnkHFbdCoRABb1XA4hydlfQ9X08p4uQRBUF_13-U4Hj8G5POmOVwBtt1NfrrdwnwmpR6ZkaWktz3AyBhXh62MY95aJ-PWpOVeGQqeOYbNDtBg0wBScYmqCw5JU-JA/s1978/pafa_cold_thk500_14day.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1236" data-original-width="1978" height="250" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEghBWvXqmPZQ628qS8ALrdRLAYCLYp6OjalI90giNz20RvIWZWMtRZKPkpNw82jh0AnkHFbdCoRABb1XA4hydlfQ9X08p4uQRBUF_13-U4Hj8G5POmOVwBtt1NfrrdwnwmpR6ZkaWktz3AyBhXh62MY95aJ-PWpOVeGQqeOYbNDtBg0wBScYmqCw5JU-JA/w400-h250/pafa_cold_thk500_14day.png" width="400" /></a></div><br /><p>Finally, it's interesting to observe that two quite extreme cold spells occurred in the last 20 years when we look at a 30-day average: late February and early/mid March of 2007, and January of 2012.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjtYVHIc2MkEZ0d-QKY4bSzrqU7-WXZrVvPrM6cIc7b4IycvYFs-gSE4qQtUSbSb8QRPWyTM1KekDQ4seifOesIJBhibzgJFiKpgCgPd4taIpTtqgOi_89y3k7-BOUS7KNBu6iKr0uAOxecuZDZHqz_UDK8-wcu9qO1fZQtuQXHgF4vSssASx9bFI0fr8M/s1952/pafa_cold_thk500_t850_30day.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1228" data-original-width="1952" height="251" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjtYVHIc2MkEZ0d-QKY4bSzrqU7-WXZrVvPrM6cIc7b4IycvYFs-gSE4qQtUSbSb8QRPWyTM1KekDQ4seifOesIJBhibzgJFiKpgCgPd4taIpTtqgOi_89y3k7-BOUS7KNBu6iKr0uAOxecuZDZHqz_UDK8-wcu9qO1fZQtuQXHgF4vSssASx9bFI0fr8M/w400-h251/pafa_cold_thk500_t850_30day.png" width="400" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgjgti6HxwITZ35884keTRCl10btKAcxRCGEo49_OIROuddwrHijcKwZpt31Nto9RqpVQ5gKEuPx4NZelEhUzLwVUh7Oy6zIN3IIUoqK4qM52ZclUK6bPvuROfGg-QninjIwyppPjBhadZWmdVhTighnFdQKC_c-yQH70CwcdiMZw1iaPtAM0Jrcd6OXvE/s1986/pafa_cold_thk500_30day.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1241" data-original-width="1986" height="250" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgjgti6HxwITZ35884keTRCl10btKAcxRCGEo49_OIROuddwrHijcKwZpt31Nto9RqpVQ5gKEuPx4NZelEhUzLwVUh7Oy6zIN3IIUoqK4qM52ZclUK6bPvuROfGg-QninjIwyppPjBhadZWmdVhTighnFdQKC_c-yQH70CwcdiMZw1iaPtAM0Jrcd6OXvE/w400-h250/pafa_cold_thk500_30day.png" width="400" /></a></div><br /><p>I hadn't previously realized how anomalous that 2007 event was, but in fact ERA5 shows the event having the lowest 30-day average temperature since 1950, by both metrics (thickness and 850mb temp above Fairbanks). Given that it was so late in the winter, the surface temperatures were nowhere near as low as they would have been a few weeks earlier; but nevertheless March 2007 was the second coldest on record in Fairbanks, and 27 of 31 days had a low of -10°F or lower (the highest such number for the month).</p><p>Here's a look at the 500mb height pattern for the 30-day period: what a classic!</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgjlQJFX2b4nx4hAbKoQe0ranF6yHc5bAFJIMgGeewdta3ZWPxW8gaNa6PrdCPS32oDPrrxAkAqpsKM7WEtJVdT5TdnWM69Lvy2b4AB-rMRzOf99caMkSy058DRQZnZVnrTZcpVDbsiWtZKUvBlXU3FyZqLx3PNFgqc5CqqSH-4tH3UPyuh6nmfMEMQ470/s1050/compday.nvaFy4y9Cr.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="813" data-original-width="1050" height="310" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgjlQJFX2b4nx4hAbKoQe0ranF6yHc5bAFJIMgGeewdta3ZWPxW8gaNa6PrdCPS32oDPrrxAkAqpsKM7WEtJVdT5TdnWM69Lvy2b4AB-rMRzOf99caMkSy058DRQZnZVnrTZcpVDbsiWtZKUvBlXU3FyZqLx3PNFgqc5CqqSH-4tH3UPyuh6nmfMEMQ470/w400-h310/compday.nvaFy4y9Cr.gif" width="400" /></a></div><br /><p>The 500mb height anomaly:</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEghVOw1rnUG37hlF1vP06_lwTV1a1uN5PCV8lzydipzzhZScinZ9ln5Jzy08-dBVmMxL6pRbQnyHdRHa7Be7yZAQWxtWAJa6UH-pe5teyf-1oD1NmZ6ZuyuIiie0EkEgAYIysVER1ukszh_BFRO942WhnF9e3igCHHsNwsohBunMdsetl9jjPrrqHVI-HA/s1050/compday.__sh_aR4Hn.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="813" data-original-width="1050" height="310" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEghVOw1rnUG37hlF1vP06_lwTV1a1uN5PCV8lzydipzzhZScinZ9ln5Jzy08-dBVmMxL6pRbQnyHdRHa7Be7yZAQWxtWAJa6UH-pe5teyf-1oD1NmZ6ZuyuIiie0EkEgAYIysVER1ukszh_BFRO942WhnF9e3igCHHsNwsohBunMdsetl9jjPrrqHVI-HA/w400-h310/compday.__sh_aR4Hn.gif" width="400" /></a></div><br /><p>And the 850mb temperature anomaly, according to the older (but still basically reliable) NCEP reanalysis:</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj_iUSKAyC7wGTp-q-il1mdOsxvJxONDuz3iyq0Pm5uCzU5kSsog7BgsRb8c6Nx7TdzX8luHljLhd8g7huAeV1zORcdsImTEMBVXU37sKt2Mw6tbOfN5K2V0kwU04FgRyPtgZ8xEIU9pHES1QqMxBEPv7-vjH8Z6YNtezutMqaJ0NT0oorqDD8zs6oObuI/s1050/compday.0HuFL0Fqon.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="813" data-original-width="1050" height="310" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj_iUSKAyC7wGTp-q-il1mdOsxvJxONDuz3iyq0Pm5uCzU5kSsog7BgsRb8c6Nx7TdzX8luHljLhd8g7huAeV1zORcdsImTEMBVXU37sKt2Mw6tbOfN5K2V0kwU04FgRyPtgZ8xEIU9pHES1QqMxBEPv7-vjH8Z6YNtezutMqaJ0NT0oorqDD8zs6oObuI/w400-h310/compday.0HuFL0Fqon.gif" width="400" /></a></div><br /><p><br /></p>Richard Jameshttp://www.blogger.com/profile/08313902028896263276noreply@blogger.com5tag:blogger.com,1999:blog-4572286363399496963.post-55927664624745054332024-02-16T17:51:00.003-09:002024-02-16T17:53:41.942-09:00The Pendulum SwingsIn the world of weather, extremes tend to beget extremes, and sometimes in the same place after only a short interval. Alaska has seen a wholesale reversal from the cold of late January and early February to very unusual warmth in the past few days.<div><br /></div><div style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgxZDpKzXa1_lBzosxhfCZD-DtAf5z7sJOvIDzs8uozpfQtsS8RLUmCTj4wtwVKSpPSOtJeaSk0NrkoCbqZxDBvDR0V6X3uGH3e1SdCZ8cvGk7OMySCkgO1-SOZtnUUXSNyYlgJ6b2pfKXCmtqPeSWBFXqPzS8_YXNxUMMAD7f2QlHQMCV1Jm3j6qS5eQM/s2000/Statewide_Temperature_Index.png"><img border="0" data-original-height="1300" data-original-width="2000" height="260" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgxZDpKzXa1_lBzosxhfCZD-DtAf5z7sJOvIDzs8uozpfQtsS8RLUmCTj4wtwVKSpPSOtJeaSk0NrkoCbqZxDBvDR0V6X3uGH3e1SdCZ8cvGk7OMySCkgO1-SOZtnUUXSNyYlgJ6b2pfKXCmtqPeSWBFXqPzS8_YXNxUMMAD7f2QlHQMCV1Jm3j6qS5eQM/w400-h260/Statewide_Temperature_Index.png" width="400" /></a></div><div>Wednesday was quite extreme, with chinook winds producing widespread 40s and some 50s downstream of the Alaska Range:</div><div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgb9AUlHqX1dfe0zqQL0jJ2e51AbZptXMhWdYzjMdSmwZimQ57bCKM4FUnAPdeHSbvLwWnGi0j6wt8S-z6WSOy4kYycEcZTk8FAVkoJ1gCS3Hl0WpSb7cAX5HK5n32uUbwcPzqs7LHgovg79hXXixdHQrLqYMfmmq1BqMGlqYqjHBhyRXr6CsZi4jk7HkA/s1403/tmax_20240214.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="844" data-original-width="1403" height="241" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgb9AUlHqX1dfe0zqQL0jJ2e51AbZptXMhWdYzjMdSmwZimQ57bCKM4FUnAPdeHSbvLwWnGi0j6wt8S-z6WSOy4kYycEcZTk8FAVkoJ1gCS3Hl0WpSb7cAX5HK5n32uUbwcPzqs7LHgovg79hXXixdHQrLqYMfmmq1BqMGlqYqjHBhyRXr6CsZi4jk7HkA/w400-h241/tmax_20240214.jpg" width="400" /></a></div><br /><div>Nenana reached 52°F, the highest temperature in February since 1943. Only February 24, 1943, had a higher temperature there in February: 54°F, and on that same day in 1943 Fairbanks reached 50°F, its record high for the month.</div><div><br /></div><div>The Fairbanks sounding on Wednesday afternoon reported a remarkable temperature of 9.4°C about 1500 feet above ground. There are only a few historical events with a temperature that high at any level in a February sounding from Fairbanks, the most recent being in 2010. It's not surprising then that the Little Chena Ridge SNOTEL site above Fairbanks (2000' elevation) reached 50°F, and Teuchet Creek (1640') reached 49°F.</div><div><br /></div><div>There'll be no prizes for guessing the mid-atmosphere flow pattern giving rise to the heat: a ridge over southeastern Alaska, with strong southerly flow coming up all the way from the sub-tropics. Here are two different views of the 500mb height (pressure) pattern on Wednesday.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi5rbKwevRs_Dhyphenhyphengvri_QOLpAF4WVFyzCo6iipOz8P7Q7SC6WXMBXcRzpMP3EPyD2djkywDrErDg0lHHFTDb_PKYJhn1AP4_lD1zeuWmqeMD_jAenZNLjnwRvm1-nIoscVj1ZihjCqQudj7YP8vjhglAv29JFpb83TuOvl1gEDD8qAe2cxdKKXFjtSYwFE/s1050/compday.R1MjFQ_KQD.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="813" data-original-width="1050" height="310" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi5rbKwevRs_Dhyphenhyphengvri_QOLpAF4WVFyzCo6iipOz8P7Q7SC6WXMBXcRzpMP3EPyD2djkywDrErDg0lHHFTDb_PKYJhn1AP4_lD1zeuWmqeMD_jAenZNLjnwRvm1-nIoscVj1ZihjCqQudj7YP8vjhglAv29JFpb83TuOvl1gEDD8qAe2cxdKKXFjtSYwFE/w400-h310/compday.R1MjFQ_KQD.gif" width="400" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGnAConSsps1C70nFQTtvm-84bGtcqJgSpwEKLIaTwBLQsLkGVJqZfteK4yE7m98UlDeL0rfMZw9mnMyvve3ZOgs6498Z-uszjqP-QV_deJFpO_pCro6v_O9hbFgm95SBhfa3Q_pz3tOQFJD913KQtC4uuj5LCWgfZitSzLcvBqqHgH3Cg28PLxx0DYXc/s1257/z500.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="827" data-original-width="1257" height="264" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGnAConSsps1C70nFQTtvm-84bGtcqJgSpwEKLIaTwBLQsLkGVJqZfteK4yE7m98UlDeL0rfMZw9mnMyvve3ZOgs6498Z-uszjqP-QV_deJFpO_pCro6v_O9hbFgm95SBhfa3Q_pz3tOQFJD913KQtC4uuj5LCWgfZitSzLcvBqqHgH3Cg28PLxx0DYXc/w400-h264/z500.png" width="400" /></a></div><br /><div>The deep trough far to the south of western Alaska was a key feature here, because it allowed that southerly flow to tap into very warm air from a low latitude. That deep trough in turn was connected to a strong west-east jet stream across the central Pacific to the north of Hawaii: winds in excess of 80 m/s, or 180mph. And this feature - an enhanced jet stream heading east into the southern US states - is very typical of El Niño. So you can thank (or blame) El Niño for the big warm-up in Alaska.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiKrttA1NH38eiN_QB9_KjRThLOHcqq64Q88hEmN8qOgxqvWp2CCS2p6UzjyhDlqQ33VkuysbgiNHZZ7jDTfdYZgo8cf-q1uhc8qSwbnSRPlO-KM8mkTmNVKJEzKR9MZzpVBXPwcr1euSwMl9D2pK-NsavzH-FE51A-fii3qFmAhpoG1-hSUDT5AzHMpyQ/s1050/compday.AM3KySvv6L.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="813" data-original-width="1050" height="310" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiKrttA1NH38eiN_QB9_KjRThLOHcqq64Q88hEmN8qOgxqvWp2CCS2p6UzjyhDlqQ33VkuysbgiNHZZ7jDTfdYZgo8cf-q1uhc8qSwbnSRPlO-KM8mkTmNVKJEzKR9MZzpVBXPwcr1euSwMl9D2pK-NsavzH-FE51A-fii3qFmAhpoG1-hSUDT5AzHMpyQ/w400-h310/compday.AM3KySvv6L.gif" width="400" /></a></div><br /><div><br /></div></div>Richard Jameshttp://www.blogger.com/profile/08313902028896263276noreply@blogger.com2tag:blogger.com,1999:blog-4572286363399496963.post-31440455162909241802024-02-13T12:26:00.000-09:002024-02-13T12:26:13.224-09:00January Climate Data<p>Taking a look back at January now that all the usual climate data is available, it was a month with a lot of variability, both in space and time. Broadly speaking, the first half was mild and the second half was cold for the state as a whole, but as usual that mostly reflects the large mainland area, not peripheral regions like the southeast panhandle. Here's the UAF statewide temperature index since November 1; despite the very unusual cold in the last 10 days of January, the average index value since November 1 is still positive (warmer than normal).</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjEt4P7gi4mipUdmtjg_kjJJqhac8Y4YuT0dxOm8nh29Dk6iMyMQvC1UD4qDK9so6bjprprJzetPpV1914CkBRvghJcfmH_b4I0wGI55Ad1p4obs0fNky5vk2-zUSAvVGb0eoeTWZzESooh1Ky-UHEUVQrJOOvlX5nog8XOGBeZsWZ60avPvvmif0c4aZ0/s2000/Statewide_Temperature_Index.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1300" data-original-width="2000" height="260" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjEt4P7gi4mipUdmtjg_kjJJqhac8Y4YuT0dxOm8nh29Dk6iMyMQvC1UD4qDK9so6bjprprJzetPpV1914CkBRvghJcfmH_b4I0wGI55Ad1p4obs0fNky5vk2-zUSAvVGb0eoeTWZzESooh1Ky-UHEUVQrJOOvlX5nog8XOGBeZsWZ60avPvvmif0c4aZ0/w400-h260/Statewide_Temperature_Index.png" width="400" /></a></div>There was also a major temperature gradient between interior Alaska versus western Alaska and the North Slope:<div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjMYe1DzI-dRCLiuLqgYKPVWgZVqyBgR3RupxcEWsmjlmE5oxFrvX9jpRlisF2ecyETttzqTdI8AbGZUyIZzdnh2jrKA1ODjAG_OVlx5aK_kpuvVVoYpDblS1WBB2kZmwBrBSL3Os0hV1-y7Ajtp0TibRG0PN-NM8FmvK8JgvRidf_ItTHsbXV2GFjJxhA/s770/akt2m_2024_1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="770" height="311" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjMYe1DzI-dRCLiuLqgYKPVWgZVqyBgR3RupxcEWsmjlmE5oxFrvX9jpRlisF2ecyETttzqTdI8AbGZUyIZzdnh2jrKA1ODjAG_OVlx5aK_kpuvVVoYpDblS1WBB2kZmwBrBSL3Os0hV1-y7Ajtp0TibRG0PN-NM8FmvK8JgvRidf_ItTHsbXV2GFjJxhA/w400-h311/akt2m_2024_1.png" width="400" /></a></div><br /><div>The epicenter of cold was in the Porcupine River drainage of the northeast, with the region around Old Crow in the Yukon being particularly cold. Old Crow itself reported -50°F or lower on 9 days and reached -61°F on the 26th; it was the coldest calendar month since 2009. In contrast, Utqiaġvik had its 8th warmest January on record.</div><div><br /></div><div>Precipitation was highly variable too:</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhYvvZsh7n3u7UBITYZayLogrFuVCKYWtc7A1v4ji-5GhpagKeLiKXYGoJIowrf59C20VoW6Hfn8wtZLJxIwDdA0gvfD3sShTdw41A1NSnJlOv5qO5pDHU9YFoJuCVPNMR_Labp4I6yJFL6QaAClgo94XoheqzcQ-RU0n_uT9MYQaRW950RPNpBzJO0PgU/s770/akpcp_2024_1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="770" height="311" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhYvvZsh7n3u7UBITYZayLogrFuVCKYWtc7A1v4ji-5GhpagKeLiKXYGoJIowrf59C20VoW6Hfn8wtZLJxIwDdA0gvfD3sShTdw41A1NSnJlOv5qO5pDHU9YFoJuCVPNMR_Labp4I6yJFL6QaAClgo94XoheqzcQ-RU0n_uT9MYQaRW950RPNpBzJO0PgU/w400-h311/akpcp_2024_1.png" width="400" /></a></div><div><br /></div>The contrast between a wet northern Panhandle (e.g. <a href="https://ak-wx.blogspot.com/2024/01/huge-snows-in-juneau.html">record snows in Juneau</a>) and dry southern Panhandle was significant. There was also major variability on a scale too small to be picked up by the ERA5 data: Rick Thoman notes that Anchorage airport actually had its 10th wettest January since 1954, and yet every other site in the region had below-normal precipitation. Here's Rick's monthly summary:<div><br /></div><div><a href="https://alaskaclimate.substack.com/p/january-2024-arctic-and-alaska-climate">https://alaskaclimate.substack.com/p/january-2024-arctic-and-alaska-climate</a></div><div><br /></div><div><br /><div>Wind was well above normal for nearly all of western and northern Alaska. It's a bit surprising to see above-normal wind with unusual cold for the northeastern interior; I would expect a cold January to be relatively calm (i.e. stronger inversions).</div></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEguQWJIYTgk_sSbRpfz5mVv7tBsGI6sa3qyBaxhJww844lyFU577TisohbIqBJlZSbWZwLKWW_NW5O_vkyOoHpp_5jq-263R20fioT3YR1m7Yc91Tkx5wmIc5W08dUvl_VZzLoCnUCgnXZSJoFmfWHFRiAY_88EINL0clawFwuDS6CjmYxrasvuF7yj4oE/s770/akwspd_2024_1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="770" height="311" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEguQWJIYTgk_sSbRpfz5mVv7tBsGI6sa3qyBaxhJww844lyFU577TisohbIqBJlZSbWZwLKWW_NW5O_vkyOoHpp_5jq-263R20fioT3YR1m7Yc91Tkx5wmIc5W08dUvl_VZzLoCnUCgnXZSJoFmfWHFRiAY_88EINL0clawFwuDS6CjmYxrasvuF7yj4oE/w400-h311/akwspd_2024_1.png" width="400" /></a></div><br /><div>Here's the complex monthly-mean pressure pattern that gave rise to the major climate anomalies: low pressure over Chukotka drew warm air up over the Bering Sea and western Alaska, but high pressure centered over northwestern Canada allowed cold air to dominate at the surface for most of the Alaskan interior.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiPogKHSO45scL_yiPxtINyPavYmUowGGTK30E9tZf2XA4BgukkbBPl2ATHS013W2kBq1kgGjCkFi3pQ2ua-M4sfTR2rovBY6eT6Oi0sQQdlgzIq6KW69J5I43Ye5Zv8pCzy8APAeyEuInN4Rk_XBnil5j-6EZHYuoFJTY1kM91-ssdqc_CbAC7ZFz6j_4/s1027/ERA5.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="688" data-original-width="1027" height="268" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiPogKHSO45scL_yiPxtINyPavYmUowGGTK30E9tZf2XA4BgukkbBPl2ATHS013W2kBq1kgGjCkFi3pQ2ua-M4sfTR2rovBY6eT6Oi0sQQdlgzIq6KW69J5I43Ye5Zv8pCzy8APAeyEuInN4Rk_XBnil5j-6EZHYuoFJTY1kM91-ssdqc_CbAC7ZFz6j_4/w400-h268/ERA5.png" width="400" /></a></div><br /><div>Looking more broadly across the Arctic, January was a mixed bag there too: much warmer than normal in Canada (but not breaking monthly records), but colder than normal in northern Scandinavia.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgqLimyE8tqmCnmXzInuQYhfHxwXC48z-kHDmIX_fmdUQWiKhRerUfXvHpbi7F1B6DXVuBuCAJld_raN76mbwHOiyY_e0tgiXq1CHprsLNrMwziQnb9lulZlj1b5RSNTy8_sBRzYp76ba9HTvtSEqduMbPm6I5nhmCTVr6fZkGcOy4UWn0QkrNXvipD8C0/s900/arcticanom_2024_1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="669" data-original-width="900" height="297" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgqLimyE8tqmCnmXzInuQYhfHxwXC48z-kHDmIX_fmdUQWiKhRerUfXvHpbi7F1B6DXVuBuCAJld_raN76mbwHOiyY_e0tgiXq1CHprsLNrMwziQnb9lulZlj1b5RSNTy8_sBRzYp76ba9HTvtSEqduMbPm6I5nhmCTVr6fZkGcOy4UWn0QkrNXvipD8C0/w400-h297/arcticanom_2024_1.png" width="400" /></a></div><br /><div><br /></div>Richard Jameshttp://www.blogger.com/profile/08313902028896263276noreply@blogger.com2tag:blogger.com,1999:blog-4572286363399496963.post-68318248419416241112024-02-09T13:47:00.002-09:002024-02-09T16:26:14.924-09:00Follow-up on Cold<p>A couple of quick items of follow-up regarding the recent cold snap. First, here's a look at temperatures in the hills above Fairbanks, using data from several of the SNOTEL sites (not all of them have been reporting data lately). The two distinct waves of cold are evident - the first culminating in the January 27 cold, and the second reaching its nadir 6 days later, on February 2.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgxt5sw30vOtGv7AFFyNwiQYYXDlFJsMX3EUjinRmXGJqSfVamI7xBUHsDrBLFTy9EAalKclqu_AQcDu9n9jEOtdf0cZvkJSo5lciTxW8u2iYCOZtbLOp5F36LxT9nlqUEC0g1YDOo3k9RjxxIht8igIQQqtdmcRAqOqAM8USsWfGKezwi-TOSzXk8S-5I/s1956/snotel_cold_snap_202401.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1255" data-original-width="1956" height="256" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgxt5sw30vOtGv7AFFyNwiQYYXDlFJsMX3EUjinRmXGJqSfVamI7xBUHsDrBLFTy9EAalKclqu_AQcDu9n9jEOtdf0cZvkJSo5lciTxW8u2iYCOZtbLOp5F36LxT9nlqUEC0g1YDOo3k9RjxxIht8igIQQqtdmcRAqOqAM8USsWfGKezwi-TOSzXk8S-5I/w400-h256/snotel_cold_snap_202401.png" width="400" /></a></div><br /><p>The second cold wave was colder at valley level, with Fairbanks seeing its first daily-mean temperatures below -40° since 2017. But some of the SNOTEL sites were no colder in the second round, and so the temperature inversion was stronger. The climatological average inversion at this time of year is about 10-11°F between Fairbanks and most of these sites, although Little Chena Ridge runs a few degrees warmer (as in this event). So the inversion was roughly normal in the second cold wave, but was certainly weaker than normal on January 27.</p><p>We can't confirm the temperature profile for February 2, because the NWS balloon sounding auto-launchers are automatically disabled below -40°, but the 3pm January 27 Fairbanks sounding confirms a total lack of inversion in the lowest 1500 feet or so.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjT1xdJWaofEtwi7ccBP50WOmWyq5quLFSj93Jgb87B0bs28t01UuaKgHnHO0cS7LSRccz7aLlhnD2MWryzW5gmEMYUu5-AQwKCDyUres8CvbtMEQrK5uKBzHNFP2fatr7NlitRAJCm2tK4tsqlG2jTn84xqEzLd7-uaI595YF0QxxuORBwvt-voW8o5GU/s1170/2024012800.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="900" data-original-width="1170" height="308" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjT1xdJWaofEtwi7ccBP50WOmWyq5quLFSj93Jgb87B0bs28t01UuaKgHnHO0cS7LSRccz7aLlhnD2MWryzW5gmEMYUu5-AQwKCDyUres8CvbtMEQrK5uKBzHNFP2fatr7NlitRAJCm2tK4tsqlG2jTn84xqEzLd7-uaI595YF0QxxuORBwvt-voW8o5GU/w400-h308/2024012800.jpg" width="400" /></a></div><br /><p>Rick Thoman comments and explains on his blog:</p><p><a href="https://alaskaclimate.substack.com/p/late-january-2024-cold-snap-in-alaska">https://alaskaclimate.substack.com/p/late-january-2024-cold-snap-in-alaska</a></p><p><br /></p><p>Rick also comments that late January may have been the coldest in the hills since February 1999, based on data from Keystone Ridge and the Fairbanks soundings. Certainly the -40° on Keystone Ridge on January 27 was the lowest minimum temperature since February 5, 1999, but it's worth mentioning also late January 2012, which saw a high temperature below -30°F on Keystone Ridge (not seen in the recent event).</p><p>Looking at the SNOTEL historical data, we get the following comparison for coldest daily mean temperature (°F) in the two years (2024 vs 2012):</p><p>Eagle Summit: -30.0 (2024) vs <span style="color: #2b00fe;">-38.5</span> (2012)</p><p>Munson Ridge <span style="color: #2b00fe;">-35.5</span> vs -33.5</p><p>Mt Ryan -31.5 vs <span style="color: #2b00fe;">-33.5</span></p><p>Upper Nome Creek <span style="color: #2b00fe;">-39.5</span> vs -39.0</p><p>Little Chena Ridge -32.0 vs -32.0</p><p><br /></p><p>With the exception of Eagle Summit (which was much colder in 2012 and also colder in other recent years), I'd say it's a toss-up: the recent cold was comparable to 2012 at elevation.</p><p>Rick's copious notes from January 2012 (the coldest month statewide since pre-1925) are worth perusing:</p><p><a href="https://ak-wx.blogspot.com/2012/01/more-cold_29.html">https://ak-wx.blogspot.com/2012/01/more-cold_29.html</a></p><p><br /></p>Richard Jameshttp://www.blogger.com/profile/08313902028896263276noreply@blogger.com0tag:blogger.com,1999:blog-4572286363399496963.post-53244835015701508292024-02-05T14:05:00.001-09:002024-02-05T14:05:40.880-09:00Cold in ContextNow that the cold snap is in the past, there will be lots of opportunity for post-mortem analysis when I have a chance (and when I ditch the nasty bug I'm suffering from). For now, I just wanted to follow-up with a final number on the weekly temperature index that I used last week to show the lack of Fairbanks-Bettles severe cold in recent decades:<div><br /></div><div><a href="https://ak-wx.blogspot.com/2024/01/cold-snaps-in-el-nino.html">https://ak-wx.blogspot.com/2024/01/cold-snaps-in-el-nino.html</a></div><div><br /></div><div>Here's the updated chart:</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhNcR9kqQCM-V727zBUpwNhm5KzAbeDqmctTZi0uOL67JT4Lf6IWk_3W2Yo9sKhyTIalE2TzY5eKSxWySY-O46zdT2S8zSbY5GYIqMyr514_YPMY_vLc0NNqQF35Pec3xZS-6IdBXjd-bPuAbXdq_l7HEAKjTP_RsfPXl-a41k7fzoBfCeHG3U6sFLc3OQ/s1832/cold_snaps_7day.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1240" data-original-width="1832" height="271" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhNcR9kqQCM-V727zBUpwNhm5KzAbeDqmctTZi0uOL67JT4Lf6IWk_3W2Yo9sKhyTIalE2TzY5eKSxWySY-O46zdT2S8zSbY5GYIqMyr514_YPMY_vLc0NNqQF35Pec3xZS-6IdBXjd-bPuAbXdq_l7HEAKjTP_RsfPXl-a41k7fzoBfCeHG3U6sFLc3OQ/w400-h271/cold_snaps_7day.png" width="400" /></a></div><br /><div>The recent steep uptrend was indeed broken, but on a 7-day time scale the coldest week was not at all unusual by historical standards.</div><div><br /></div><div>However, the cold spell was more notable in the end for its longevity than its severity at any one time, and so there's a more significant cold anomaly on a 14-day time scale:</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhIs0khG2S-YgY3RTHJybpme2e6vN5u38U9zxY7bGVjzncg4NnaDtiT1LfmWeDebVXivIDtlKXEm0OKYjd_ecNgqjcU0lPE5NPps6EmgAEE5yshsBtiWnVVPxvwHHNcS6H8gKYCbP1oVtE10JwQyZqVGXq8YOdfiQgnjE4xrNFBek62-6s84cDCU-jafxc/s1838/cold_snaps_14day.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1235" data-original-width="1838" height="269" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhIs0khG2S-YgY3RTHJybpme2e6vN5u38U9zxY7bGVjzncg4NnaDtiT1LfmWeDebVXivIDtlKXEm0OKYjd_ecNgqjcU0lPE5NPps6EmgAEE5yshsBtiWnVVPxvwHHNcS6H8gKYCbP1oVtE10JwQyZqVGXq8YOdfiQgnjE4xrNFBek62-6s84cDCU-jafxc/w400-h269/cold_snaps_14day.png" width="400" /></a></div><br /><div>Here we see a most remarkable absence of 14-day cold in recent years - almost as if the climate never recovered from the record-warm winter of 2015-16 (during the last very strong El Niño!). The lack of variability since 2016-17 is quite amazing.</div><div><br /></div><div>But the cold snap just ended is a significant change. Only 15 winters since 1950 had a colder 14-day period for these two climate observing sites.</div><div><br /></div><div>Here's the 500mb height anomaly for the 13 days that had average temperature below -30°F for Fairbanks and Bettles combined.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjVitxlgA8_qTWUaKmflpPOMBDDy8R8EtFZh3Z7ve0Sy6gH_vXrR-tYsqtTZwRKCz4o7vSY9SjazyszGVekza-nlZXRC4FVyR0vYraPieDBOGsD0m4B7bw-AYDxR2oQ7BrYh9GN0-yb4Uc5uJTvWYAlBoZC33q3VOUe0AfK0G2UKCGk61CyEbi3Z_Q7F0U/s1050/compday.KoELcVnfXr.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="813" data-original-width="1050" height="310" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjVitxlgA8_qTWUaKmflpPOMBDDy8R8EtFZh3Z7ve0Sy6gH_vXrR-tYsqtTZwRKCz4o7vSY9SjazyszGVekza-nlZXRC4FVyR0vYraPieDBOGsD0m4B7bw-AYDxR2oQ7BrYh9GN0-yb4Uc5uJTvWYAlBoZC33q3VOUe0AfK0G2UKCGk61CyEbi3Z_Q7F0U/w400-h310/compday.KoELcVnfXr.gif" width="400" /></a></div>This too is interesting, because the mid-atmosphere anomaly is right over the northern interior; and while we might expect that to be true, in fact significant cold in Fairbanks is more often associated with a trough over western Canada. This too will be a topic for follow-up.<br /><div><br /></div>Richard Jameshttp://www.blogger.com/profile/08313902028896263276noreply@blogger.com2tag:blogger.com,1999:blog-4572286363399496963.post-78576702217809073302024-02-02T18:06:00.002-09:002024-02-03T07:05:01.554-09:00Deep Cold<p>Today's high temperature (so far) of <strike>-39°F</strike> -38°F at Fairbanks airport is the coldest in 7 years, and it's the coldest February day since 1999. Since 1930, only two years have seen a daily high temperature this cold in Fairbanks in February: 1947 and 1999. It also happened in 1910, according to the Ag Farm data.</p><p>As for the low temperature, -49°F this morning was also the coldest in Fairbanks since 2017; but there's a chance -50°F could be reached before midnight, with the 5pm temperature already back down to -45°F. [Update: it was reached]</p><p>Unfortunately there's no sounding data to look at the vertical profile of temperature, because the automated balloon launcher is disabled when the temperature reaches -40°. This is a great pity, in my view, and a loss to science. If the automated launcher can't operate, then perhaps some hardy soul could be persuaded to launch a balloon manually, as in the old days - like 7 years ago. Here's the sounding from 3pm on January 18, 2017, the last date Fairbanks saw a high temperature below -40°F (the lowest levels aren't included on the plot, but the data was recorded.)</p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhtxMukZRGB9n6GfvMVCpxDZG1mwIeblNxV65tOO6AkW5Hnyb_xfPsvp3hO39FPLkC_rjtm8kjlRojosYfco8vQd0f9uCNCqqZk_-W3KsQI8ZPOUSv7jYJdH6ApVLaRG-EIcWwbQHobmmczH3mrzxvSsIDGoMX_v7Gx7Bv3dKEpemx2GYS00ejb6JbBBx8/s680/2017011900.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="680" data-original-width="680" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhtxMukZRGB9n6GfvMVCpxDZG1mwIeblNxV65tOO6AkW5Hnyb_xfPsvp3hO39FPLkC_rjtm8kjlRojosYfco8vQd0f9uCNCqqZk_-W3KsQI8ZPOUSv7jYJdH6ApVLaRG-EIcWwbQHobmmczH3mrzxvSsIDGoMX_v7Gx7Bv3dKEpemx2GYS00ejb6JbBBx8/w400-h400/2017011900.png" width="400" /></a></div><br /><p>The 2017 cold snap was much shorter than the current one, but was briefly severe, with more widespread -50s than any day in the current cold spell. There's a series of posts in the blog archives, e.g.</p><p><a href="https://ak-wx.blogspot.com/2017/01/cold-snap.html">https://ak-wx.blogspot.com/2017/01/cold-snap.html</a></p><p>Here's a splendid photo published to Twitter today by Cody Moore, showing ice fog filling the valley from a vantage point on UAF's West Ridge:</p><p><a href="https://twitter.com/codymoorewx/status/1753549093471998281">https://twitter.com/codymoorewx/status/1753549093471998281</a></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiDq9LWLNTL-VVTnSgyA3SANqnYxJPJzSfhsplaNYA7CpExsRTQq01T8nTxieZULK1yQ8MWrElCoCOX3eruXYaXx6ETTrSfKyH61yhUf0uZweaJWHnrGh92xahwGELK_9nKsCVAIz7Nr3jTS8rhgbknXdRnLoxc4xDkbtpbaTvryF7H9LCB4yYaRJOsArY/s2048/GFXbmm3aMAAJpal.jpeg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1536" data-original-width="2048" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiDq9LWLNTL-VVTnSgyA3SANqnYxJPJzSfhsplaNYA7CpExsRTQq01T8nTxieZULK1yQ8MWrElCoCOX3eruXYaXx6ETTrSfKyH61yhUf0uZweaJWHnrGh92xahwGELK_9nKsCVAIz7Nr3jTS8rhgbknXdRnLoxc4xDkbtpbaTvryF7H9LCB4yYaRJOsArY/w400-h300/GFXbmm3aMAAJpal.jpeg" width="400" /></a></div><br /><p>Visibility at the airport has been 1/4 - 1/2 mile for most of the day. Water vapor emissions from the urban environment are to blame for the fog, with a substantial contribution from the power plant plumes; here's another photo, this time from UAF GINA:</p><p><a href="https://twitter.com/uafgina/status/1753493360315437259">https://twitter.com/uafgina/status/1753493360315437259</a></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg3P7U2lhyM_lOBH_u4YJcVxK_PZZl-fyuoyCPl8QktJiSugM33o_SEzM8H-lpMznab2_D71lkpzYZ3U5CQ1Ytx1d2ox4HbS-WrjIRmuwZilqepIDRux95TDyDDc35RFhFtZbSiDxv_7R7QMWVsVLwBhvFivQkLOVCKMJwHqn5ca6M6DVl2nFxVLA_p_Ik/s2040/icefog.jpeg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1536" data-original-width="2040" height="301" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg3P7U2lhyM_lOBH_u4YJcVxK_PZZl-fyuoyCPl8QktJiSugM33o_SEzM8H-lpMznab2_D71lkpzYZ3U5CQ1Ytx1d2ox4HbS-WrjIRmuwZilqepIDRux95TDyDDc35RFhFtZbSiDxv_7R7QMWVsVLwBhvFivQkLOVCKMJwHqn5ca6M6DVl2nFxVLA_p_Ik/w400-h301/icefog.jpeg" width="400" /></a></div><br /><p>The FAA webcam on Ester Dome provides another perspective on just how localized the fog is: skies were gloriously clear across most of the interior today.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhnfjJTZnSjx1iUfEn2mVKhjh_GuSyxzOGlqzxOy18kkFIMF8s9w0UmdYO517CIkMxj7rXq1-paFj0ti4UtyVaEGdPFIvK7EZYKGO6oG_btoQ5fbeCmNTpRza58jwaulE-_7VPZ5WHVWM79rMvdUd5tm6dikdLUEcwI2gn_6XMs3jfi6n2crT61KDNva0M/s640/e1.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="480" data-original-width="640" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhnfjJTZnSjx1iUfEn2mVKhjh_GuSyxzOGlqzxOy18kkFIMF8s9w0UmdYO517CIkMxj7rXq1-paFj0ti4UtyVaEGdPFIvK7EZYKGO6oG_btoQ5fbeCmNTpRza58jwaulE-_7VPZ5WHVWM79rMvdUd5tm6dikdLUEcwI2gn_6XMs3jfi6n2crT61KDNva0M/w400-h300/e1.jpg" width="400" /></a></div><br /><p>A simple animation gives a sense of the moisture flowing from the power plants at left towards the Tanana River valley at right.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgkBw0jrsFsDLpU2f_hbOmf3j97jeyhYAOYK7EQcJbN-JVS5AD8pfCsNRtLxv0vnEB3QoNcpbpT0glzOWlIGVhVD02qzA8WrEuL-9UgeXPmAKy8lfMTVrSdVlu3HkM_FdfpFkiD1-5SB5xBaRgV08bqeYEPm9RGRxjZ965DzhCntTg5NIQeziV2QwkSu5A/s640/anim.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="480" data-original-width="640" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgkBw0jrsFsDLpU2f_hbOmf3j97jeyhYAOYK7EQcJbN-JVS5AD8pfCsNRtLxv0vnEB3QoNcpbpT0glzOWlIGVhVD02qzA8WrEuL-9UgeXPmAKy8lfMTVrSdVlu3HkM_FdfpFkiD1-5SB5xBaRgV08bqeYEPm9RGRxjZ965DzhCntTg5NIQeziV2QwkSu5A/w400-h300/anim.gif" width="400" /></a></div><br /><p><br /></p>Richard Jameshttp://www.blogger.com/profile/08313902028896263276noreply@blogger.com2tag:blogger.com,1999:blog-4572286363399496963.post-4217051450091522562024-02-01T18:01:00.003-09:002024-02-01T18:04:14.068-09:00Cold Snow<p>There's been a lot of interesting weather across Alaska in recent days - as demonstrated by the sudden uptick in blog posts - and here's another one that merits attention.</p><p>Back on Sunday, as the upper level trough pivoted over western Alaska, heavy snow developed in the frontal zone over Anchorage, even as temperatures at the surface remained uncharacteristically low. Sunday's high temperature was only +2°F even while prolonged snowfall occurred in the afternoon and through the overnight hours, leading to an accumulation of 9.9" by midnight and another 6.7" the next day (adjacent to the airport).</p><p>Such a large snowfall at such a low temperature is unprecedented in the Anchorage climate data back to 1953, and not by a small margin: check out the following chart showing the joint distribution of daily high temperatures and daily snowfall.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhm60dexZZ4IQszfXtRnQT7Ww1wrCDASi8USjAdtKsOhRdpEkTLIoIRjvVtNd_y7OW2Cv9I5Ujy7OogAsuW-sN9ZI9LyJZxp9bgqp42VC5GqBLm8kwFeaaXs1DQHDBgVCi7EnwNXU68L12m9LBciqStnpdNycEOvG5BefL6t6cQTqfL_Gf2r-7hxJJwvI8/s1825/daily_snow_vs_tmax_panc.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1201" data-original-width="1825" height="264" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhm60dexZZ4IQszfXtRnQT7Ww1wrCDASi8USjAdtKsOhRdpEkTLIoIRjvVtNd_y7OW2Cv9I5Ujy7OogAsuW-sN9ZI9LyJZxp9bgqp42VC5GqBLm8kwFeaaXs1DQHDBgVCi7EnwNXU68L12m9LBciqStnpdNycEOvG5BefL6t6cQTqfL_Gf2r-7hxJJwvI8/w400-h264/daily_snow_vs_tmax_panc.png" width="400" /></a></div><br /><p>The explanation for this outcome involves the rare combination of strong mid-atmospheric lift along the frontal zone, combined with an unusually cold airmass at the surface. Here's the Anchorage airport sounding at 3pm on Sunday:</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgODCmiMr37HHsrCpLAh2ClU5VIDLXzgs7hmqJRiiqtESK0nOG49pvgzx82p1YxE8MSk5swIbtrnNFzqcwKp_OE6uEec-p4iinou2vQXI80Nvb1BLvGIbkDbxoLPAa8opEubgaXSXHRf6vFFc-sRhyphenhyphenRJjVhL7dADB8WeevWTk_t7OFqBNeP2vj6mtQjm9Q/s800/2024012900.70273.skewt.parc.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="640" data-original-width="800" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgODCmiMr37HHsrCpLAh2ClU5VIDLXzgs7hmqJRiiqtESK0nOG49pvgzx82p1YxE8MSk5swIbtrnNFzqcwKp_OE6uEec-p4iinou2vQXI80Nvb1BLvGIbkDbxoLPAa8opEubgaXSXHRf6vFFc-sRhyphenhyphenRJjVhL7dADB8WeevWTk_t7OFqBNeP2vj6mtQjm9Q/w400-h320/2024012900.70273.skewt.parc.png" width="400" /></a></div><br /><p>Notice the cold layer at the surface, with northerly winds of over 30mph at about 2500' above ground. But higher up the winds were out of the southeast and south, and the sounding shows a deep layer of saturated (humid) air near or just below -10°C, which is a temperature conducive to growth of dendritic snow crystals.</p><p>Here's a map of 850mb temperatures (shaded) at the same time, showing the extremely cold air to the north and west, and much warmer air to the southeast of Anchorage; the snow occurred in the strong gradient between the two.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhX6W7IgCBMkenIy7cj9LHmcCJBrQctd0Xkl-wyZYigQcNzUlNaHLS-8ZOQ7d8_GM-rqA9RCPrClRgTUTNgM7jvNPmGxHCIlB6Dek37yJSwUQ6Fn9jPjOAGaygcekdoAg347F82RWR_z88Sdd5A2UB8UxA0HioApH1-4DAlpdIbzGqg4gYqd9GVrhzI5wc/s1024/gfs_T850_ak_1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="809" data-original-width="1024" height="316" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhX6W7IgCBMkenIy7cj9LHmcCJBrQctd0Xkl-wyZYigQcNzUlNaHLS-8ZOQ7d8_GM-rqA9RCPrClRgTUTNgM7jvNPmGxHCIlB6Dek37yJSwUQ6Fn9jPjOAGaygcekdoAg347F82RWR_z88Sdd5A2UB8UxA0HioApH1-4DAlpdIbzGqg4gYqd9GVrhzI5wc/w400-h316/gfs_T850_ak_1.png" width="400" /></a></div><br /><p>And the 500mb height analysis at the same time:</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGIK3ccH6W-aA0w1jc55zn_iB15qCN77JDqkw-DSjxk22gGTXlKW7517r8LUNUyrG68tdeQ1wpuPWIJKV5hCDVEMzMJ-WvL9SrvAtc8_J_J6m5A1L18eI22VSnwCQkCCs5_8Vy3uCQ61Re1wLoFlt7G8SpQlir4m_QSAgv325-8csBfSqN9yvjY8Hh9bs/s1024/gfs_z500a_ak_1.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="809" data-original-width="1024" height="316" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjGIK3ccH6W-aA0w1jc55zn_iB15qCN77JDqkw-DSjxk22gGTXlKW7517r8LUNUyrG68tdeQ1wpuPWIJKV5hCDVEMzMJ-WvL9SrvAtc8_J_J6m5A1L18eI22VSnwCQkCCs5_8Vy3uCQ61Re1wLoFlt7G8SpQlir4m_QSAgv325-8csBfSqN9yvjY8Hh9bs/w400-h316/gfs_z500a_ak_1.png" width="400" /></a></div><br /><p>It's interesting to note that Fairbanks and Bettles also saw accumulating snow to an unusual degree for such cold weather. In Fairbanks the daily total was only 0.6" - also on Sunday - but nevertheless this tied the record for most snow with such a cold high temperature (-27°F). In Bettles 4.9" fell on Monday, with a high temperature of -13°F.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEidiKK_72o1Sc_UbOtM8NP4GaH7pKywpz8fs6ltJNsPr-vT9sS4Mm4vdbrJc-jevANCKZvqVslOIs53uosOwHFPHt-k_48TreUjmNlKZmrf2FBABXKOE-1U18VHb9qhdBW6uTWFBtXES03KiJd9gAd_CKs6vWKQmqauZyYnVy_fjPso57qHsdMB6Rhtx5c/s1824/daily_snow_vs_tmax_pafa.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1207" data-original-width="1824" height="265" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEidiKK_72o1Sc_UbOtM8NP4GaH7pKywpz8fs6ltJNsPr-vT9sS4Mm4vdbrJc-jevANCKZvqVslOIs53uosOwHFPHt-k_48TreUjmNlKZmrf2FBABXKOE-1U18VHb9qhdBW6uTWFBtXES03KiJd9gAd_CKs6vWKQmqauZyYnVy_fjPso57qHsdMB6Rhtx5c/w400-h265/daily_snow_vs_tmax_pafa.png" width="400" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhRizkjmfP4gAUVss-Ob5QcusYzDJQOPUBJvJvESdCqf5HASgGHAs_aVLh8LPARszEdFulC2ko4u2vtRsqaXaYDAyH5DrMiEm2aoqVfkE6iSQtYNoRx79xLNTLtdl202JKqaiURXqLVKS2LO_QVajJVvUNF5dfabYI43Oyp5yUTNtG9ltdqjU3YBZD8Rhk/s1820/daily_snow_vs_tmax_pabt.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1210" data-original-width="1820" height="266" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhRizkjmfP4gAUVss-Ob5QcusYzDJQOPUBJvJvESdCqf5HASgGHAs_aVLh8LPARszEdFulC2ko4u2vtRsqaXaYDAyH5DrMiEm2aoqVfkE6iSQtYNoRx79xLNTLtdl202JKqaiURXqLVKS2LO_QVajJVvUNF5dfabYI43Oyp5yUTNtG9ltdqjU3YBZD8Rhk/w400-h266/daily_snow_vs_tmax_pabt.png" width="400" /></a></div><br /><p><br /></p>Richard Jameshttp://www.blogger.com/profile/08313902028896263276noreply@blogger.com4tag:blogger.com,1999:blog-4572286363399496963.post-25850424142029792752024-01-30T18:00:00.000-09:002024-01-30T18:00:08.549-09:00Airmass Contrasts<p>[Hat-tip to Brian Brettschneider for pointing out the event discussed below.]</p><p>Yesterday I highlighted the strong southerly flow across central and eastern Alaska that raised temperatures aloft up to near the freezing point above Fairbanks. Elevated locations in the Yukon-Tanana uplands and the Alaska Range experienced this warmth directly: take a look at yesterday's high temperatures between Delta Junction and Glennallen (click to enlarge).</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgEEBy-Q3gpMarcrd4ST-abDqaUrIQqHr8JFgw7pS0P-JJg4gPUaAE4TxOcjc8VX81hW76CWOx8IOER3liRDiitFJijWTnke3Lb8j0HLywfQv4zjv1xSK9y8iRhCAVeVmIa9AYrCKYKa0d8YzM75okyjxZ6GXPDvIKY6U0WO_77pRhBDoyYZTGXz8r-MLU/s1607/tmax_20240129.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="847" data-original-width="1607" height="211" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgEEBy-Q3gpMarcrd4ST-abDqaUrIQqHr8JFgw7pS0P-JJg4gPUaAE4TxOcjc8VX81hW76CWOx8IOER3liRDiitFJijWTnke3Lb8j0HLywfQv4zjv1xSK9y8iRhCAVeVmIa9AYrCKYKa0d8YzM75okyjxZ6GXPDvIKY6U0WO_77pRhBDoyYZTGXz8r-MLU/w400-h211/tmax_20240129.jpg" width="400" /></a></div><br /><p>An automated site just above 5000' elevation (Look Eyrie) overlooking Isabel Pass (3600') rose to 36°F around noon:</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvaHvrmGjtrQo7p3JFD0E3cb0O_dyBmmRSBdp4RSYHz7cwwbnw3nBWwZ4kD5gGzOWa3_tiFAEGbrfKx2kvZLRPJnYYsllSVmkXy19y1AEyUpPiXBm0grBO4SAwwbOACbgRSIZUfreJ7Uhh3odRJPgCDJ_wrfoYAsCdxDznHUcb2Evd3JKkuVoPwpq7VtU/s1200/lesa2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="1200" height="266" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvaHvrmGjtrQo7p3JFD0E3cb0O_dyBmmRSBdp4RSYHz7cwwbnw3nBWwZ4kD5gGzOWa3_tiFAEGbrfKx2kvZLRPJnYYsllSVmkXy19y1AEyUpPiXBm0grBO4SAwwbOACbgRSIZUfreJ7Uhh3odRJPgCDJ_wrfoYAsCdxDznHUcb2Evd3JKkuVoPwpq7VtU/w400-h266/lesa2.png" width="400" /></a></div><br /><p>But below about 3000' on the north side of the Alaska Range, the warmth didn't break through. Here's the chart for a site at 2430' (Black Rapids Chalet) just to the north of the Richardson Highway pass: notice the high temperature of -17°F yesterday.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiTL8tLHWpg5SjVJrWJYZT3hV_LElAr-Jg5u1p9liecafno5VlKaEfNXvKkEEz_sA4zkI-cWM4cr4YAhnGhxinFAkJXVerpLnhARfSoZuhJr1bk2KVKJ3r7CYqpTRWoEvIssHutxtwKM6k1HzrIQsTn16q-LYC0bJq-KJCIvWBjyv2YFQMRCqPI4gjL1u4/s1200/bkca2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="1200" height="266" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiTL8tLHWpg5SjVJrWJYZT3hV_LElAr-Jg5u1p9liecafno5VlKaEfNXvKkEEz_sA4zkI-cWM4cr4YAhnGhxinFAkJXVerpLnhARfSoZuhJr1bk2KVKJ3r7CYqpTRWoEvIssHutxtwKM6k1HzrIQsTn16q-LYC0bJq-KJCIvWBjyv2YFQMRCqPI4gjL1u4/w400-h266/bkca2.png" width="400" /></a></div><br /><p>In the roughly 10 miles and 1000' elevation between this site and the pass, the back-and-forth "slosh" of the dense surface cold air produced remarkable swings in temperature yesterday evening. The following chart is from the Black Rapids FAA site less than 2 miles up the road, and just 250' higher:</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgcQDbOd8cVACEIDiN8IFkAxhGKoglrRkQXi61VjUFpOtB-h5oPg1UWEIcD1PVMrh7-ERJ1pr2JI2tkNOBUoMXqzk3MiOTBjCxR9q8jP3qua1VR-doWZlwQrCale7L5oqqjXu_x6DeN6IHRbYD5AVeDmuCFeyIxBSjoa9jQRX2FouevUYn_pv6hxAE8nP4/s1200/5bkwc.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="1200" height="266" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgcQDbOd8cVACEIDiN8IFkAxhGKoglrRkQXi61VjUFpOtB-h5oPg1UWEIcD1PVMrh7-ERJ1pr2JI2tkNOBUoMXqzk3MiOTBjCxR9q8jP3qua1VR-doWZlwQrCale7L5oqqjXu_x6DeN6IHRbYD5AVeDmuCFeyIxBSjoa9jQRX2FouevUYn_pv6hxAE8nP4/w400-h266/5bkwc.png" width="400" /></a></div><br /><p>Check out the alternating wind direction and temperatures between 9pm and midnight (click to enlarge):</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiRmGHjAQz-g-MC4YjVvQ1MAW3CO5G7G5CX6qRsAB3bw7jizYd3u6hGuX7CykdV-0WToKJgv9t2optS7C4Bfh4gv7bZCHAId0986viQsFm-VbfjQQOB4rcu80oNyJ1IIWwi84l-Kr81eXD8oJUMq0XiaP4UcuhQhkRGxnaySxX8EihaKp16s4ark04SNiA/s832/5bkwc.table.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="832" data-original-width="489" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiRmGHjAQz-g-MC4YjVvQ1MAW3CO5G7G5CX6qRsAB3bw7jizYd3u6hGuX7CykdV-0WToKJgv9t2optS7C4Bfh4gv7bZCHAId0986viQsFm-VbfjQQOB4rcu80oNyJ1IIWwi84l-Kr81eXD8oJUMq0XiaP4UcuhQhkRGxnaySxX8EihaKp16s4ark04SNiA/w235-h400/5bkwc.table.png" width="235" /></a></div><br /><p>Warm air broke through 3 separate times, with the temperature dropping back to -10°F or lower between each episode! Then finally the cold northerly flow won out by midnight, and the temperature re-stabilized below -20°F, with quite a wind chill (wind speed up to 35mph).</p><p>Up at the pass, a single warm episode occurred, with the temperature holding not far below freezing for more than 5 hours in a southerly breeze; then the wind reversed and the temperature dropped an amazing 42°F in 10 minutes. In reality one can imagine the temperature drop being almost instantaneous as the boundary passed: air masses of such different density are nearly immiscible, like oil and water - hardly mixing at all.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjMtlF-yPlRXat_EQmeiFVmqO4LwwJe3m6qQ0O7NCfE4tBCIyZkJF7y-TIZuHF53CY2uIzhH5VTN2374QqlXUvYFuOQ0TEY-_W1_Lw_gnKV9-4F64xAddtx9zTqELUq3R6GxKF9wdKaOfcTdPl8EeCQHIQkCnygBcmLPACiAICExUBZG7i-KrTMJRkZJkI/s1200/z32wc.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="1200" height="266" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjMtlF-yPlRXat_EQmeiFVmqO4LwwJe3m6qQ0O7NCfE4tBCIyZkJF7y-TIZuHF53CY2uIzhH5VTN2374QqlXUvYFuOQ0TEY-_W1_Lw_gnKV9-4F64xAddtx9zTqELUq3R6GxKF9wdKaOfcTdPl8EeCQHIQkCnygBcmLPACiAICExUBZG7i-KrTMJRkZJkI/w400-h266/z32wc.png" width="400" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhj3P0LBVo0QQpyFvNZ7d8OtW69pSRkXU9GUuTXzGP7vxN5Se14-udhEtUeYRUBWKY1fTraVDzmdA0ScRehJP5A4wtGY-drXzpG93PVj_O4APm1crird6qSbNSJAjp3NLz7jH1xxHvQX7YPnkYHn9WtZvSVUeVVGQZH_Ojl0HLuXSqbZYLuWAOkdnAqz9g/s832/z32wc.table.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="832" data-original-width="489" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhj3P0LBVo0QQpyFvNZ7d8OtW69pSRkXU9GUuTXzGP7vxN5Se14-udhEtUeYRUBWKY1fTraVDzmdA0ScRehJP5A4wtGY-drXzpG93PVj_O4APm1crird6qSbNSJAjp3NLz7jH1xxHvQX7YPnkYHn9WtZvSVUeVVGQZH_Ojl0HLuXSqbZYLuWAOkdnAqz9g/w235-h400/z32wc.table.png" width="235" /></a></div><br /><p>Similar events occurred about 15 miles to the south, at Fielding Lake (elevation 3000'):</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjZ_12ta4Gt16mJo4eKIoGxFlL9Apvvw9jujsjG4qj2QjxH7b0lVjZhAe7ItmlUUeoIIUWSvaxVi4-KWMjBJ6eJXkrr6cwLZdZ7cS5clA4ofinKnIoet1hoNveoZj8etPNmJVHbEAJa8Y7NJ0PEbGjZzY9xlPghLM_E9QTItuZZ08Q7dpIuAyBeO7Q2QSo/s617/flda2.table.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="617" data-original-width="270" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjZ_12ta4Gt16mJo4eKIoGxFlL9Apvvw9jujsjG4qj2QjxH7b0lVjZhAe7ItmlUUeoIIUWSvaxVi4-KWMjBJ6eJXkrr6cwLZdZ7cS5clA4ofinKnIoet1hoNveoZj8etPNmJVHbEAJa8Y7NJ0PEbGjZzY9xlPghLM_E9QTItuZZ08Q7dpIuAyBeO7Q2QSo/w175-h400/flda2.table.png" width="175" /></a></div><br /><p>Here's the surface/MSLP analysis at 3pm, courtesy of Environment Canada.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhY3y8uwIvZ3KE0jn9a67synT3_T5UJ1_CqrXyMFjuQOX23j-Kfs_4sFNneA5Bme8WufaaWLx6eoR90gslPmPhXpw-L7kSvR1Mbb6ismiJ2FR2u7KaPWV898dl5K7dMFUPFxcHYlaX4s1iIzqOcG3qfkqd0an_TTMjfZjbL6vypci4Zo4so-kqLTl1yMSQ/s925/mslp.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="823" data-original-width="925" height="356" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhY3y8uwIvZ3KE0jn9a67synT3_T5UJ1_CqrXyMFjuQOX23j-Kfs_4sFNneA5Bme8WufaaWLx6eoR90gslPmPhXpw-L7kSvR1Mbb6ismiJ2FR2u7KaPWV898dl5K7dMFUPFxcHYlaX4s1iIzqOcG3qfkqd0an_TTMjfZjbL6vypci4Zo4so-kqLTl1yMSQ/w400-h356/mslp.png" width="400" /></a></div><br /><p>Low pressure was pushing up from the Gulf (producing another big snowfall in Anchorage), and the impulse associated with this storm is what drove the temporary warm air intrusion across the higher elevations.</p><p>What an interesting meteorological event!</p>Richard Jameshttp://www.blogger.com/profile/08313902028896263276noreply@blogger.com3tag:blogger.com,1999:blog-4572286363399496963.post-85814463726637656262024-01-29T18:10:00.006-09:002024-01-29T18:12:37.141-09:00Cold Moves West<p>The axis of the cold trough aloft has shifted westward in the past couple of days - towards a more climatologically favorable position - and therefore southerly flow has developed across the central and eastern interior, bringing clouds, widespread light snow, and relatively warmer temperatures. This morning's 500mb analysis:</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjHjyIWV9qfqPeI3kV7OR2PY6a6hAg2qg8sSBXY7ciDRLen66FSm_VHoHVYi7fpeZXoj0jg4lyG5TwpWz6JVFC_ZFoubosQfH836zYPXSOtgho8MrlLy0-gAhWddUT_r4qVYrDyJYlrUS8eyaWlC_48oKe8CbO_-f3POImT2ZbXK964fglpwzSUHST8tyM/s1023/z500.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="839" data-original-width="1023" height="328" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjHjyIWV9qfqPeI3kV7OR2PY6a6hAg2qg8sSBXY7ciDRLen66FSm_VHoHVYi7fpeZXoj0jg4lyG5TwpWz6JVFC_ZFoubosQfH836zYPXSOtgho8MrlLy0-gAhWddUT_r4qVYrDyJYlrUS8eyaWlC_48oKe8CbO_-f3POImT2ZbXK964fglpwzSUHST8tyM/w400-h328/z500.png" width="400" /></a></div><br /><p>Accordingly, the core of the surface-level cold has moved to western and southwestern Alaska. One of the more notable cold spots this morning was Unalakleet on the Norton Sound coast: the temperature dropped to -45°F with a light southeasterly breeze as cold drained out of the interior. This appears to be the lowest temperature in Unalakleet since February 1999. The all-time record there (with data since 1941) is an almost unfathomable -59°F, which occurred almost exactly 35 years ago during the great 1989 cold snap. A number of interior spots dropped into the -70s in that event, making the current cold snap look paltry.</p><p>There's more cold to come later this week as an arm of the trough reloads over eastern Alaska, but so far the coldest readings I've seen are -57°F at Fort Yukon, Bettles, and the Norutak Lake RAWS; -58°F at Tanana; and -59°F at the Allakaket FAA site. (As an aside, the North Pole 1N co-op site has been reporting ridiculous numbers below -60°F and is not credible at all.)</p><p>So far I've not seen a daily high temperature of -50°F or lower. Bettles came close yesterday, with a daylight high of -50°F, but clouds rolled in before midnight, lifting the temperature by a full 20°F after dark.</p><p>Here are some of today's low temperatures (the online map is too large to fit in one screen capture): </p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhTQjRHzPA3XVjpRgy4BoIpCUERWFtLZpQF_CkvlAmcDXPOjpOLGFx1Qcy_R4w8gMWt7HgFSLLwxxRKRQW6TR31sz6iv5lEBJjY1oMEVEckJ6QejgUYgyEJPJonsMDILOPLXtVXLOVy6xX9kaHIiG8HvX1XBh0rPkklrpaWUqG7HftFGrZiYailzPuqQWE/s1437/tmin_north.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="843" data-original-width="1437" height="235" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhTQjRHzPA3XVjpRgy4BoIpCUERWFtLZpQF_CkvlAmcDXPOjpOLGFx1Qcy_R4w8gMWt7HgFSLLwxxRKRQW6TR31sz6iv5lEBJjY1oMEVEckJ6QejgUYgyEJPJonsMDILOPLXtVXLOVy6xX9kaHIiG8HvX1XBh0rPkklrpaWUqG7HftFGrZiYailzPuqQWE/w400-h235/tmin_north.jpg" width="400" /></a></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh3pqNSn5coLX8ALFioL7P4MvhPhzXF8KTqJdF2mtKXawUKzae3Ru7D_ozhM83QieZH4eET8t26QdVHbHLdE5lPZlODVtPO81PC2IfJ9MCo4MQVifY-gfrjvo8V-yzPPxZx-KKB72kZxavz498vdEliSMGmzKG8EdWWa9LWP803Cb4FttlpiLDgKYtSilM/s1437/tmin_south.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="843" data-original-width="1437" height="235" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh3pqNSn5coLX8ALFioL7P4MvhPhzXF8KTqJdF2mtKXawUKzae3Ru7D_ozhM83QieZH4eET8t26QdVHbHLdE5lPZlODVtPO81PC2IfJ9MCo4MQVifY-gfrjvo8V-yzPPxZx-KKB72kZxavz498vdEliSMGmzKG8EdWWa9LWP803Cb4FttlpiLDgKYtSilM/w400-h235/tmin_south.jpg" width="400" /></a></div><br /><div>One more interesting note: the deep southerly flow aloft has brought temperatures to nearly the freezing point a few thousand feet above the surface, as seen in this afternoon's sounding from Fairbanks:</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg_tMTLgMIUjWqMxFLJk45J1ovWjXz4ns52KxJIS5JvoNpL5hLuP7oJQXm-X25IuTp7rtqo3uWSZkYYwcFOXxTNeZp47DFdb2Ye-OFDVW4lo30U0LEXHWX4gFiS_QlkKvZJzhGb5uWbhn-LABVHj4ic9m_4aO1dw4FXyB6JCfazgDxMisaeKiDfxY4rfhg/s1170/2024013000.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="900" data-original-width="1170" height="308" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg_tMTLgMIUjWqMxFLJk45J1ovWjXz4ns52KxJIS5JvoNpL5hLuP7oJQXm-X25IuTp7rtqo3uWSZkYYwcFOXxTNeZp47DFdb2Ye-OFDVW4lo30U0LEXHWX4gFiS_QlkKvZJzhGb5uWbhn-LABVHj4ic9m_4aO1dw4FXyB6JCfazgDxMisaeKiDfxY4rfhg/w400-h308/2024013000.jpg" width="400" /></a></div><br /><div>The 32.4°C temperature inversion between 916mb and 800mb is one of the greatest inversions ever observed in the history of Fairbanks soundings. The all-time record (data since 1948) is 33.4°C, observed in December 1956 and February 2018. Here's my post from the 2018 event:</div><div><br /></div><div><a href="https://ak-wx.blogspot.com/2018/02/extreme-inversions.html">https://ak-wx.blogspot.com/2018/02/extreme-inversions.html</a></div><div><br /></div>Richard Jameshttp://www.blogger.com/profile/08313902028896263276noreply@blogger.com0tag:blogger.com,1999:blog-4572286363399496963.post-34731532009982304712024-01-27T18:16:00.005-09:002024-01-27T18:49:20.917-09:00Cold Snaps in El Niño<p>The cold snap appears to be reaching its nadir this weekend for the western and northern interior. This morning's temperatures bottomed out in the -50s Fahrenheit for many locations from as far south as Nikolai up to the Kobuk River valley and eastward to the Yukon Flats. The coldest spots in Fairbanks-land dropped to near or just below -50°F, although the airport only made it to -40°.</p><p>With more than a month having passed since the solstice, afternoon sunshine allowed for temperatures to recover somewhat this afternoon, but less so in the northern interior, and Bettles saw a high temperature of -47°F. It's fairly late on the calendar for this: the latest date in Bettles with such a cold high temperature is February 3rd (1993).</p><p>This morning's 500mb chart from Environment Canada shows the mid-atmosphere situation, with a deep, cold trough over central and northern Alaska.</p><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><br /></div><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgqPtwoCn9Lwa7seD7ugoSzeeztb0qnvO9JEvKR3Vutl8VbyTf3PnD4jlKJ0A0YYrq52_g0kh1KOjKkAV6AQshtOOFaQ-hPXyQ4y8wbgQz_m0p_IzMVZZ-St4-K-zZ6fopQA6Hl02vg0y5jGn2JoFK9C2Tcapy8OQid3CYpwz2BHZgv_hyphenhyphenOGY4HijPSIHo/s1023/z500.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="836" data-original-width="1023" height="328" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgqPtwoCn9Lwa7seD7ugoSzeeztb0qnvO9JEvKR3Vutl8VbyTf3PnD4jlKJ0A0YYrq52_g0kh1KOjKkAV6AQshtOOFaQ-hPXyQ4y8wbgQz_m0p_IzMVZZ-St4-K-zZ6fopQA6Hl02vg0y5jGn2JoFK9C2Tcapy8OQid3CYpwz2BHZgv_hyphenhyphenOGY4HijPSIHo/w400-h328/z500.png" width="400" /></a></div><br /><p>This afternoon's 500mb height of 4950m on the Fairbanks sounding is the lowest in 7 years.</p><p>I mentioned the other day (prompted by Rick Thoman's comment) that really significant cold snaps are relatively uncommon during El Niño winters. Here's a look at some data to illustrate that point: the chart below shows each winter's lowest weekly (7-day) mean temperature for Fairbanks and Bettles combined (i.e. the average of the two sites). The colors indicate El Niño or La Niña winters, as defined by the December-January Multivariate ENSO Index being above +0.5 or below -0.5 respectively.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiLE7cUUlMUUZRy8rj-_68nPCExULrWg9UfWYqZD1Vuv4utOJh56cgM6y4WCGU9UcWtvzCGT12UCFJsOp5XAvySOo32sBGkH9ifxV1Nc0atRlt27tWgSCsH1N8sPofgaY6gS1OJrG_gClG33apq_bO9a3hGpGjTzhdcYJm1lYn6nNCfiprfinkOV5K-KAc/s2014/cold_snaps_vs_enso.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1239" data-original-width="2014" height="246" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiLE7cUUlMUUZRy8rj-_68nPCExULrWg9UfWYqZD1Vuv4utOJh56cgM6y4WCGU9UcWtvzCGT12UCFJsOp5XAvySOo32sBGkH9ifxV1Nc0atRlt27tWgSCsH1N8sPofgaY6gS1OJrG_gClG33apq_bO9a3hGpGjTzhdcYJm1lYn6nNCfiprfinkOV5K-KAc/w400-h246/cold_snaps_vs_enso.png" width="400" /></a></div><br /><p>It's clear that for the seven decades as a whole, La Niña winters have tended to produce colder cold spells, although admittedly the evidence is only compelling from about 1980 through 2010. In the 1950s, 60s, and 70s there were some nasty cold spells with El Niño, and in recent years La Niña hasn't produced anything like the cold that it used to.</p><p>The result is similar if we classify years based on the Oceanic Nino Index, which uses only Niño3.4 SSTs as an index of ENSO strength.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEijfu1kei_vLRY9wzMPZFahENw7Ew12sV2s1LRJwjSc90PkQDtGoEsOwNgGNb1WZ7Sv5qmTIaOvAMs0lxNcC5l4xLu0EVzlvb0epLtx3zrhLQuAJWyyLIcky6GoUuWtnimeuWMWzawT72VF0ga2kQ7uFuT7QjnQ3h_CLDpDr-XH7wf110nmvhadaEwhexo/s2018/cold_snaps_vs_enso_oni.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1242" data-original-width="2018" height="246" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEijfu1kei_vLRY9wzMPZFahENw7Ew12sV2s1LRJwjSc90PkQDtGoEsOwNgGNb1WZ7Sv5qmTIaOvAMs0lxNcC5l4xLu0EVzlvb0epLtx3zrhLQuAJWyyLIcky6GoUuWtnimeuWMWzawT72VF0ga2kQ7uFuT7QjnQ3h_CLDpDr-XH7wf110nmvhadaEwhexo/w400-h246/cold_snaps_vs_enso_oni.png" width="400" /></a></div><br /><p>Either way, we find a difference of about 5-6°F on average between the coldest weeks in El Niño versus La Niña winters; but there is obviously a lot of variability between winters, and from decade to decade.</p><p>The disappearance of the most severe cold in recent decades is remarkable. Here's a chart showing all winters:</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjnpVUS67HNWXVJbtf1lWg6gWv1S4MChxc2AkbuH1ezLlQMSdPZRSIC5cgo3MtY-ORORQK5gNyfiY4fvsxOmycBugARRck3tMVpcX8JX-Peml7nbO-kej6r9N0qo_sc1z6Dklhh50YIWr_AVN6gJ5dZkTUicmhNK-PhsvD5QdKKb12Ceg7yLqz2tCTIe0g/s1821/cold_snaps.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1239" data-original-width="1821" height="272" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjnpVUS67HNWXVJbtf1lWg6gWv1S4MChxc2AkbuH1ezLlQMSdPZRSIC5cgo3MtY-ORORQK5gNyfiY4fvsxOmycBugARRck3tMVpcX8JX-Peml7nbO-kej6r9N0qo_sc1z6Dklhh50YIWr_AVN6gJ5dZkTUicmhNK-PhsvD5QdKKb12Ceg7yLqz2tCTIe0g/w400-h272/cold_snaps.png" width="400" /></a></div><p>The current cold snap will break the sharp uptrend, but perhaps only marginally; we'll see.</p><p>The Fairbanks urban heat island is certainly a factor here, but the trend is only about 20% greater for Fairbanks than it is for Bettles (+1.8°F/decade vs +1.5°F/decade for the coldest weekly temperatures).</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiFe8rJoBpFcPojwcm0I5QrSx6Y5PMExPyxyIbxzoRfQ3nSPxQL7kEdrHwqRHubUq4rnFqqHHDmZGyL_zVoulbDtSTv6No5giY-sCP4jnAj1m9kynUNAGcEhVAQBO_0UuZBXvdJy60COdYEVSnAtF28zNbd_oxsWitAphLq8psi8MwBlI3SV6sIHSUx8TQ/s1808/cold_snaps_pafa.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1242" data-original-width="1808" height="275" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiFe8rJoBpFcPojwcm0I5QrSx6Y5PMExPyxyIbxzoRfQ3nSPxQL7kEdrHwqRHubUq4rnFqqHHDmZGyL_zVoulbDtSTv6No5giY-sCP4jnAj1m9kynUNAGcEhVAQBO_0UuZBXvdJy60COdYEVSnAtF28zNbd_oxsWitAphLq8psi8MwBlI3SV6sIHSUx8TQ/w400-h275/cold_snaps_pafa.png" width="400" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi-UCDjWhkn_KjQ801dPL0R7F9ZoTj1zszOaXk2gB9eFzvn46d8e0AsAXeyxnCAC94P6hq29DF4fZt2kX7MK2H0IYR-aG1pQuatM59GlJjR2JuIrbBzbD5QhsKCRtnc2X0MdOPVzChmczUkV-n4TRdHp5ozp3jA-IkxLqd4em9VFayCf1cN_KLd6LDgKoU/s1807/cold_snaps_pabt.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1237" data-original-width="1807" height="274" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi-UCDjWhkn_KjQ801dPL0R7F9ZoTj1zszOaXk2gB9eFzvn46d8e0AsAXeyxnCAC94P6hq29DF4fZt2kX7MK2H0IYR-aG1pQuatM59GlJjR2JuIrbBzbD5QhsKCRtnc2X0MdOPVzChmczUkV-n4TRdHp5ozp3jA-IkxLqd4em9VFayCf1cN_KLd6LDgKoU/w400-h274/cold_snaps_pabt.png" width="400" /></a></div><br /><p><br /></p>Richard Jameshttp://www.blogger.com/profile/08313902028896263276noreply@blogger.com5tag:blogger.com,1999:blog-4572286363399496963.post-28166913245111118192024-01-24T17:52:00.001-09:002024-01-24T17:52:56.823-09:00Huge Snows in JuneauBack in November, Anchorage saw a remarkable snow onslaught (38" or so) that amounted to the 3rd greatest on record for a time scale of 10-14 days:<div><br /></div><div><a href="https://ak-wx.blogspot.com/2023/11/south-coast-snowstorm.html">https://ak-wx.blogspot.com/2023/11/south-coast-snowstorm.html</a></div><div><br /></div><div><a href="https://ak-wx.blogspot.com/2023/11/a-few-notes.html">https://ak-wx.blogspot.com/2023/11/a-few-notes.html</a><br /><div><br /></div><div>Juneau has now countered with a yet more extreme snow situation, with two huge storms in the space of 10 days, and a 12-day total of 64". This is the greatest snow accumulation on record for windows of 11-18 days, and it's well ahead of the previous record for 12-day snowfall:</div></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7zNbDqBFhoeeGe3J8hGPloXT73Gh2-zf5itJBquAVMEyWZNUxUOQE3Oc7QyACPDTw7R7LKZkt8VYcO-PL8k64cpGEeAvq_xmIiCdHgoBzTGkHgEhA8LB-7B5dXP01IdlSOiKjnO6SRuTMuZZaEfe5RhW4SxvcgUJ7uY3gHIRagQMiXYDLAlhRPvB9tXw/s490/juneau_12day_snowfall.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="455" data-original-width="490" height="371" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7zNbDqBFhoeeGe3J8hGPloXT73Gh2-zf5itJBquAVMEyWZNUxUOQE3Oc7QyACPDTw7R7LKZkt8VYcO-PL8k64cpGEeAvq_xmIiCdHgoBzTGkHgEhA8LB-7B5dXP01IdlSOiKjnO6SRuTMuZZaEfe5RhW4SxvcgUJ7uY3gHIRagQMiXYDLAlhRPvB9tXw/w400-h371/juneau_12day_snowfall.png" width="400" /></a></div><br /><div><br /></div><div>The latest 3-day total of 34.5" at Juneau airport is itself the 3rd greatest on record, exceeded only by storms in 1963 and 1966. Even higher amounts were reported from other locations, including 48" around the corner on Taku Inlet.</div><div><br /></div><div>According to the NWS, "Juneau Docks and Harbors Department reported several boats capsized or sunk by weight of the snow".</div><div><br /></div><div>The key aspect of the weather setup seems to have been a near-stationary frontal zone draped across Southeast Alaska: below are the surface analysis charts from 3pm Sunday, Monday, and Tuesday respectively. Notice the long stationary front marked on the top image and resurrected on the last image, with broad areas of low pressure over the Gulf and modest high pressure to the east and north.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjX1eWK6GVINWxVj_94WHqo2L_mPqJ8-rf-n1qvKRCZR4JxY1wHWBTYVmJl3OEz3k4dsmFLJ5VRVz2lq6e2WHljvPv8-y5MeJiLjTvCfTGrHx38O_Fqa2bnKn_LAvRh2KzwZBpSgFDISXL8Yupqy-kf2k_q6yhoSKHKZm9OHTqrz3aHZJLdJdBUERVjHtc/s926/mslp1.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="628" data-original-width="926" height="271" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjX1eWK6GVINWxVj_94WHqo2L_mPqJ8-rf-n1qvKRCZR4JxY1wHWBTYVmJl3OEz3k4dsmFLJ5VRVz2lq6e2WHljvPv8-y5MeJiLjTvCfTGrHx38O_Fqa2bnKn_LAvRh2KzwZBpSgFDISXL8Yupqy-kf2k_q6yhoSKHKZm9OHTqrz3aHZJLdJdBUERVjHtc/w400-h271/mslp1.png" width="400" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjMWlPJAovyMu0aFbUWMtKcJg-8H9A0tOX7pjPElw6eXlFUozdNYgOG54T6MW0MnKzJ3NdhnaUpA3nr20YZuFv_hw5IudaZpf-rrAJRqMJLKmcfbEcbZPbeHVpuiseNdgqfGMIV3E17VdpcMHiN68FaqICqlUY2zfQPTJ1x65RUYu0mVnSCDX2HjasAT0A/s926/mslp2.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="628" data-original-width="926" height="271" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjMWlPJAovyMu0aFbUWMtKcJg-8H9A0tOX7pjPElw6eXlFUozdNYgOG54T6MW0MnKzJ3NdhnaUpA3nr20YZuFv_hw5IudaZpf-rrAJRqMJLKmcfbEcbZPbeHVpuiseNdgqfGMIV3E17VdpcMHiN68FaqICqlUY2zfQPTJ1x65RUYu0mVnSCDX2HjasAT0A/w400-h271/mslp2.png" width="400" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj4o1OWwdZMuFZRHEr1xzjCumOkPogWFGILZcvWC3uOTovjjcEidGim-NF-IhP49yaqQCBYonQo55iR_3zHaE-qgsyv8DR_udy1WvUrza0VY3buYwcXnuIpMCLzIyoMlgYUD8zJ3NlrIzV2mIL4tw8A5N8IbxS_ZjuhXWgMnznd1Nq_DPSHEP8pFIvZyxk/s925/mslp3.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="630" data-original-width="925" height="272" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj4o1OWwdZMuFZRHEr1xzjCumOkPogWFGILZcvWC3uOTovjjcEidGim-NF-IhP49yaqQCBYonQo55iR_3zHaE-qgsyv8DR_udy1WvUrza0VY3buYwcXnuIpMCLzIyoMlgYUD8zJ3NlrIzV2mIL4tw8A5N8IbxS_ZjuhXWgMnznd1Nq_DPSHEP8pFIvZyxk/w400-h272/mslp3.png" width="400" /></a></div><br /><div>A slow-moving weather situation is obviously a prerequisite for prolonged periods of heavy precipitation. It also seems clear that the relatively weak nature of the Gulf low pressure was a key factor, because the warm southerly flow wasn't strong enough to drive out low-level cold air, and precipitation remained in the form of snow longer than expected. A stronger, more dynamic Gulf storm would have quickly swept warm air into the Panhandle and produced rain instead.</div><div><br /></div><div>From the NWS Juneau discussion on Tuesday afternoon:</div><div><br /></div><div><div>Southeast Alaska Forecast Discussion</div><div>National Weather Service Juneau AK</div><div>332 PM AKST Tue Jan 23 2024</div><div><br /></div><div>.SHORT TERM...Winter weather continues for places north of the</div><div>Icy strait corridor while places to the south continue to see</div><div>rain. Temperatures this afternoon have been slow to warm up,</div><div>especially those still under the influence of outflow winds. Model</div><div>guidance continues to try and warm up locations that are</div><div>currently seeing snow but observations continue to show cold air</div><div>remains. A wave moving up from the south has started to enter the</div><div>panhandle bringing a reinforcing shot of moisture to the area.</div><div>This wave could also bring a surge of warm up form the south to</div><div>the north as well. The big question with this remains are the</div><div>winds associated with it strong enough to mix out the surface</div><div>inversion that has allowed us to see snow. Current thinking is</div><div>that we will see a slight warm up with this wave but that it will</div><div>not be strong enough to mix out the cold air. With that being the</div><div>case, the Juneau area is expected to continue to see snow. If the</div><div>wave does succeed in mixing out the surface inversion, the snow</div><div>will switch over to rain fairly quickly. The current forecast</div><div>tried to reflect this possibility of staying snow for longer and</div><div>the winds failing to mix out the inversion until tomorrow.</div></div><div><br /></div>Richard Jameshttp://www.blogger.com/profile/08313902028896263276noreply@blogger.com0tag:blogger.com,1999:blog-4572286363399496963.post-81926406741836476302024-01-23T14:01:00.004-09:002024-01-23T14:01:54.938-09:00Cold Snap Begins<p>A significant cold snap is getting under way for interior and northern Alaska, and computer models show it deepening and intensifying in the coming days. Here's the latest ECMWF ensemble mean 500mb height anomaly forecast for Saturday afternoon, showing a deep trough with a very cold Arctic air mass parked over Alaska:</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgalVSb0IaW1yE8wT71blDL5b4ynsWCRatVxt3qUdzWeeE0S0T0MG01GA4_NlMiIt6zsstzXUTu6MUn8FhfQ2at3iqjQx-14Pp2pCrW8oJHCcu5mOFPDVeWxn14dFpmLynjWiLh1H9DHodGxHMviQJYO5bZ93_fHhm-XVyAoQLqdxxWLBoOoSC9r30G8nc/s1024/eps_z500a_ak_19.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="809" data-original-width="1024" height="316" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgalVSb0IaW1yE8wT71blDL5b4ynsWCRatVxt3qUdzWeeE0S0T0MG01GA4_NlMiIt6zsstzXUTu6MUn8FhfQ2at3iqjQx-14Pp2pCrW8oJHCcu5mOFPDVeWxn14dFpmLynjWiLh1H9DHodGxHMviQJYO5bZ93_fHhm-XVyAoQLqdxxWLBoOoSC9r30G8nc/w400-h316/eps_z500a_ak_19.png" width="400" /></a></div><br /><p>By this weekend the air aloft will be much colder than what's currently in place, even though surface temperatures dropped into the -40s in many eastern interior locations this morning. The initial round of cold has been generated by surface-based cooling (clear skies, calm winds) with a strong inversion: here's the 3am sounding from Fairbanks today.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjlUXGJ8rn8oIIAFGt_ExdKgUaWutzDzUNgjFfJqnX9uf9jFmRGIfwA3IFBiGWIsfXHDLV5VFFz2sjwbyEU6PHZzEiVOfv_nCRlyi8_YVXb7LLF6v0i-JF5WqNFCV5sx7bWRi5OeNJvP4tqfPI0b69iVHMpziwKBYW6TfIyBRQ2BiLvpvlVvinv1maY_Cs/s1170/2024012312.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="900" data-original-width="1170" height="308" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjlUXGJ8rn8oIIAFGt_ExdKgUaWutzDzUNgjFfJqnX9uf9jFmRGIfwA3IFBiGWIsfXHDLV5VFFz2sjwbyEU6PHZzEiVOfv_nCRlyi8_YVXb7LLF6v0i-JF5WqNFCV5sx7bWRi5OeNJvP4tqfPI0b69iVHMpziwKBYW6TfIyBRQ2BiLvpvlVvinv1maY_Cs/w400-h308/2024012312.jpg" width="400" /></a></div><br /><p>The cooperative observer at North Pole 1N reported an impressive -49°F this morning, while Fort Yukon dropped to -50°F. -48°F was measured over in Eagle, and Chicken saw -52°F. It looks like these numbers will be exceeded without difficulty over the next week.</p><p>If we do end up with a historically significant cold spell, it will be quite unusual for an El Niño winter; Rick Thoman notes the possibility of the longest winter cold spell during El Niño since January 1973. That was a good one: 15 consecutive days with -40° or lower in Fairbanks.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiP38jBkLsuBF6nnPdUyu0R6h1_wXfvO4wlEfAQ-ZuoxeYUfhFWVXsXUD0e_DQHCceL6bqsznLy7heC4fbZveYeijP-jL_W8lfjBG2dqZVuCP3qTd1JgJCvBh6sgzLZY2DbXcL51NPYuTqQ1_l-3q1Mi35U_AtMVft_56jTw0pL_3r9KDzByagR_oF4fb0/s800/plot.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="591" data-original-width="800" height="295" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiP38jBkLsuBF6nnPdUyu0R6h1_wXfvO4wlEfAQ-ZuoxeYUfhFWVXsXUD0e_DQHCceL6bqsznLy7heC4fbZveYeijP-jL_W8lfjBG2dqZVuCP3qTd1JgJCvBh6sgzLZY2DbXcL51NPYuTqQ1_l-3q1Mi35U_AtMVft_56jTw0pL_3r9KDzByagR_oF4fb0/w400-h295/plot.png" width="400" /></a></div><br /><p><br /></p>Richard Jameshttp://www.blogger.com/profile/08313902028896263276noreply@blogger.com4tag:blogger.com,1999:blog-4572286363399496963.post-63319275918170142322024-01-18T11:07:00.003-09:002024-01-18T11:07:44.721-09:00Bering Sea Ice<p>Rick Thoman put up a post about Arctic sea ice earlier this week, and it's well worth reading, as usual.</p><p><a href="https://alaskaclimate.substack.com/p/arctic-sea-ice-update">https://alaskaclimate.substack.com/p/arctic-sea-ice-update</a></p><p>Recent warm weather across the Bering Sea has prevented new ice growth since the turn of the year, and the latest daily ice extent number from NSIDC is nearly 20% below the median of the last 30 years. However, we're still some way above the low ice conditions of 2015 and 2017-2018; compare the latest daily map to the same date in 2018:</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEigLrbAyook1-8ELc2g8SaYTolrIcAmsgMA9zxSXvBwUhuM-m3uTNEF0lE9LnNaW_X0gEIblhG233NaNu8GxzT3RnJSui3OXPyJl3YpSSYEFKKcR6PIqVfErBkcg9titD8dn_uuq46wGM7Dbk81E3PJBlg7bNndDyZg0Otjo23EPih1XrAvSx5TmWTxAuU/s1632/CT.20240117.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1632" data-original-width="1056" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEigLrbAyook1-8ELc2g8SaYTolrIcAmsgMA9zxSXvBwUhuM-m3uTNEF0lE9LnNaW_X0gEIblhG233NaNu8GxzT3RnJSui3OXPyJl3YpSSYEFKKcR6PIqVfErBkcg9titD8dn_uuq46wGM7Dbk81E3PJBlg7bNndDyZg0Otjo23EPih1XrAvSx5TmWTxAuU/w259-h400/CT.20240117.jpg" width="259" /></a></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhFvCX8e3Gj0zA0YG3moSUGfgMtYtwu9YsTgBaoSGUbQQJhwt__CX9FkVhRicssapDkUUFQxWXIuHnKV1IaVL0UuIT904PH9QSqvYM90Yq4ssfMfAUtUu6uqcJjk6rXIP3JdiUOAkKU60Ri0HZlZWrI8c5-SkMgvYswwk8wmSxFb9j_RENBjdG11sTiiHA/s1632/CT.20180117.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1632" data-original-width="1056" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhFvCX8e3Gj0zA0YG3moSUGfgMtYtwu9YsTgBaoSGUbQQJhwt__CX9FkVhRicssapDkUUFQxWXIuHnKV1IaVL0UuIT904PH9QSqvYM90Yq4ssfMfAUtUu6uqcJjk6rXIP3JdiUOAkKU60Ri0HZlZWrI8c5-SkMgvYswwk8wmSxFb9j_RENBjdG11sTiiHA/w259-h400/CT.20180117.jpg" width="259" /></a></div><br /><p>Here's a look at daily temperature departures from normal since October 1st for Nome, Bethel, and St Paul Island:</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh2o52UvlR_c8_FCD-7Qxyr0Ou51oKyLMN9cjuJxD1fXroevhXCLc3uqIqzAA4qHVrF8K1KLtuwGuzXeI4wfg2MuFCV4b1hhHABhTI7KLvWfYlfAz4YtvBdkXJI0-AtBrdzeqQ1MIcWXD3FhuMjd1ylGdtvs_7oyBDr4n895p7J1Chfjir0KxzoJUuHwQU/s800/PAOM.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="591" data-original-width="800" height="295" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh2o52UvlR_c8_FCD-7Qxyr0Ou51oKyLMN9cjuJxD1fXroevhXCLc3uqIqzAA4qHVrF8K1KLtuwGuzXeI4wfg2MuFCV4b1hhHABhTI7KLvWfYlfAz4YtvBdkXJI0-AtBrdzeqQ1MIcWXD3FhuMjd1ylGdtvs_7oyBDr4n895p7J1Chfjir0KxzoJUuHwQU/w400-h295/PAOM.png" width="400" /></a></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgZW_Qs6mgSWAUV56NAlNxYPUTrjoECFKmmo8P4rdI02c05acPPazcFBx5SyfzGYfALhFXCWRnB6iILCz2koYC-9AesXqMMIVwL-xZ8pYj0mKg3dD_lVvQsFQMNsvhkjqlYiyvrhz-i46PzSpCB80QXf64wiDcdMgMX6fWeC7_PdQCAdt-ZTr5AM3tOmWU/s800/PABE.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="591" data-original-width="800" height="295" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgZW_Qs6mgSWAUV56NAlNxYPUTrjoECFKmmo8P4rdI02c05acPPazcFBx5SyfzGYfALhFXCWRnB6iILCz2koYC-9AesXqMMIVwL-xZ8pYj0mKg3dD_lVvQsFQMNsvhkjqlYiyvrhz-i46PzSpCB80QXf64wiDcdMgMX6fWeC7_PdQCAdt-ZTr5AM3tOmWU/w400-h295/PABE.png" width="400" /></a></div><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiKPZIGlnYE3Yjiz8C9yQHVxruoXbtVDpaNguzeYFIVuKImfwkGA7vFzmYuA8gy_kFDf9YUCASTULgbip8dhcJic_ApZ0LccJ_dhjIsi7hETtEKSoCftU-DDDDhvW3hLJqc_QXerabVxeYn-6yM7kYCgHe-lz54eHPYR1R-5DkmQanmxCpr31-W4-n9QRc/s800/PASN.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="591" data-original-width="800" height="295" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiKPZIGlnYE3Yjiz8C9yQHVxruoXbtVDpaNguzeYFIVuKImfwkGA7vFzmYuA8gy_kFDf9YUCASTULgbip8dhcJic_ApZ0LccJ_dhjIsi7hETtEKSoCftU-DDDDhvW3hLJqc_QXerabVxeYn-6yM7kYCgHe-lz54eHPYR1R-5DkmQanmxCpr31-W4-n9QRc/w400-h295/PASN.png" width="400" /></a></div></div><br /><p>December was quite chilly, as I noted <a href="https://ak-wx.blogspot.com/2024/01/december-climate-data.html">here</a>, but the rather persistent warmth since then has become a more significant and long-lived anomaly.</p><p>It's not really surprising, of course: the northwestern North Pacific is so warm, and across such a wide area, that winds from the south and west are bringing air with higher temperatures than normal. Here's the average vector wind at 850mb since January 1: lots of southerly flow across western Alaska.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjJcW7S4-a0h5qBQoH7oD29FNPpdXUuE-9RbFiVZfQYbKDKj6TklWFqs09R5a-VKd-My1JtI0gfyfa0ZbmB8hBogalRSzj3g8ddec1vlds-IZ_fq6a4yoLzBgd0jsc5NDYzBP65ctgynfFW4Resw7duOAw1sUZmmlgQM92ywsWq61T3333M8EDF7Q3sLYU/s1050/compday.3NycQyuNI8.gif" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="813" data-original-width="1050" height="310" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjJcW7S4-a0h5qBQoH7oD29FNPpdXUuE-9RbFiVZfQYbKDKj6TklWFqs09R5a-VKd-My1JtI0gfyfa0ZbmB8hBogalRSzj3g8ddec1vlds-IZ_fq6a4yoLzBgd0jsc5NDYzBP65ctgynfFW4Resw7duOAw1sUZmmlgQM92ywsWq61T3333M8EDF7Q3sLYU/w400-h310/compday.3NycQyuNI8.gif" width="400" /></a></div><br /><p>And here's the global sea surface temperature analysis from December, expressed in terms of standardized departure from normal (to reveal the local significance of the anomalies).</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhwBbKPhOsHsrN1j313HHhKvNbCNg_3SYRPUoXfPa0H1Ld9LGSQUp1LK7iokLud78imLnxOSVbcuJOpfmoLqMXTrX4Rtt6MOwzoDK232G8RJ6Rfv0SUHNukS9btDNT9aeU6e3EEwjHorI50wff5HWrHKk6SF1tOXwxbnYIlHx5aZcOp448cANomnmdgHkY/s800/sst_stdanom_202312.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="534" data-original-width="800" height="268" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhwBbKPhOsHsrN1j313HHhKvNbCNg_3SYRPUoXfPa0H1Ld9LGSQUp1LK7iokLud78imLnxOSVbcuJOpfmoLqMXTrX4Rtt6MOwzoDK232G8RJ6Rfv0SUHNukS9btDNT9aeU6e3EEwjHorI50wff5HWrHKk6SF1tOXwxbnYIlHx5aZcOp448cANomnmdgHkY/w400-h268/sst_stdanom_202312.png" width="400" /></a></div><br /><p><br /></p>Richard Jameshttp://www.blogger.com/profile/08313902028896263276noreply@blogger.com0tag:blogger.com,1999:blog-4572286363399496963.post-36282723058516833112024-01-14T11:40:00.000-09:002024-01-14T11:40:36.969-09:00Polar Vortex<p>Alaska's first -50°F measurement of the season occurred on Thursday in the well-known cold spot of Chicken, up at 1800 feet of elevation in the Fortymile country. It's been chilly in the Yukon Flats too: well into the -40s in places. In an interesting reversal of the December situation (when it was warmer to the east), this cold in eastern Alaska is just the western margin of an impressive cold pool across the border in Canada.</p><p>The cold across Canada is associated with a deep mid-atmospheric circulation that is sometimes (and controversially) known as the "polar vortex", and its migration across western Canada and then down toward the lower 48 has generated plenty of headlines. Here's what it looked like in the 500mb analysis (courtesy of Environment Canada) at 3pm Friday:</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjYgfQRPeoaIDY0XFb-tLYUbzva9GwXapWcYdoROEU7Gz-ZZliZ1Esvqxtjx6ieJkTLNOnaCF0JojP4dXHZsIFGS9jVhY9w_6q8u8ewKOD_tEYu2dr09kazVtNfh1i5cMy5yjzeZz6g13o5JfzV8RMBrIAanqTWdYZhVkP_uiEnId3cpH-giOrb8kdPI38/s1209/z500.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="910" data-original-width="1209" height="241" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjYgfQRPeoaIDY0XFb-tLYUbzva9GwXapWcYdoROEU7Gz-ZZliZ1Esvqxtjx6ieJkTLNOnaCF0JojP4dXHZsIFGS9jVhY9w_6q8u8ewKOD_tEYu2dr09kazVtNfh1i5cMy5yjzeZz6g13o5JfzV8RMBrIAanqTWdYZhVkP_uiEnId3cpH-giOrb8kdPI38/s320/z500.png" width="320" /></a></div><br /><p>Notice the sharp but strong ridge over Alaska, toward the top left of the image. Here's a hemispheric view of 850mb (lower troposphere) temperatures at about the same time, with North America on the left:</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgCOZ1pJMKlJptIMtXcfTunuOWnlGdDleE1WmlMK9vMikoq6VTALG6cAz7nwOmM4ELJnD-uCOvqv_bOyU_P0XdgXrWujuc5Pi72KEJ-Ljfrupqgf0A284j3QPIMpu0CobRRMz2u80-KwdZf2AyB0rc3GIfW7AQSaiibVUbwl09ps-N6sfQvGX5eIlyT3LU/s845/arctic_t850_prelim_20240112.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="750" data-original-width="845" height="355" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgCOZ1pJMKlJptIMtXcfTunuOWnlGdDleE1WmlMK9vMikoq6VTALG6cAz7nwOmM4ELJnD-uCOvqv_bOyU_P0XdgXrWujuc5Pi72KEJ-Ljfrupqgf0A284j3QPIMpu0CobRRMz2u80-KwdZf2AyB0rc3GIfW7AQSaiibVUbwl09ps-N6sfQvGX5eIlyT3LU/w400-h355/arctic_t850_prelim_20240112.png" width="400" /></a></div><br /><p>The coldest air mass in the hemisphere was over western Canada - even colder than over Siberia - but parts of Alaska had 850mb temperatures above freezing at the same time.</p><p>Yesterday afternoon's surface analysis shows a vast area of high pressure from Greenland and the western Canadian Arctic down to the U.S. Plains; but low pressure over western Alaska.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj1h3AW_yd0zgYsgsayTdnH9pMQTJp4uMdX4tx_EMwePtrnTjUxJcBWGbyf-1pzDUdbTrBBjI3d0N_nKU338Pokjz86EGp4p1Xypk8N-uyl7lrm6J5pmDjdVh7LPlEqZRUzY7HlNKfW6RoQ4vRPzX7eJ8e85-LKE7t8N1tmD2ZuvffrNilCYedOvj0W5Q0/s1789/mslp.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1530" data-original-width="1789" height="343" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj1h3AW_yd0zgYsgsayTdnH9pMQTJp4uMdX4tx_EMwePtrnTjUxJcBWGbyf-1pzDUdbTrBBjI3d0N_nKU338Pokjz86EGp4p1Xypk8N-uyl7lrm6J5pmDjdVh7LPlEqZRUzY7HlNKfW6RoQ4vRPzX7eJ8e85-LKE7t8N1tmD2ZuvffrNilCYedOvj0W5Q0/w400-h343/mslp.png" width="400" /></a></div><br /><p>It's ironic that the cold air of the so-called "polar vortex" is actually associated with high pressure at the surface, not the low pressure of a cyclonic circulation. But the term is a misnomer in its popular usage: the "polar vortex" more properly refers to the wintertime circulation in the stratosphere, 10-30 miles above the surface. Read more about this at NOAA's new polar vortex blog:</p><p><a href="https://www.climate.gov/news-features/blogs/polar-vortex/welcome-polar-vortex-blog">https://www.climate.gov/news-features/blogs/polar-vortex/welcome-polar-vortex-blog</a></p><p>Getting back to near-Alaska conditions, the cold in northwestern Canada has been harsh in recent days: into the -50s Fahrenheit in many locations. But despite several days in the -40s at Dawson, the Yukon River still isn't properly frozen over: here's the latest webcam image from noon today.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEikWS8do3Mtcid-iTnU2mkw0h286Tr49RHQ0O8VELj1Eq0ajBEBgBiNspRIQ12vYsT9eTYi4EzYs9IcOSQbB4aV2sx2P508HlIaxKkJdGyyx2B4CwPH55BzEDx3wjgJFoCTGrqiqP08ts94ZR8_7LUJ9l_VVVLFOuJJOEFQJW4N73YJaYjBO1nLvvYkUME/s1280/dawson.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="800" data-original-width="1280" height="250" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEikWS8do3Mtcid-iTnU2mkw0h286Tr49RHQ0O8VELj1Eq0ajBEBgBiNspRIQ12vYsT9eTYi4EzYs9IcOSQbB4aV2sx2P508HlIaxKkJdGyyx2B4CwPH55BzEDx3wjgJFoCTGrqiqP08ts94ZR8_7LUJ9l_VVVLFOuJJOEFQJW4N73YJaYjBO1nLvvYkUME/w400-h250/dawson.jpg" width="400" /></a></div><p>This is a repeat of the no-freeze-up difficulty of several recent years, with no ice road crossing between West Dawson and the main town. There's a trail crossing upstream:</p><p><a href="https://ca.news.yahoo.com/dawson-city-residents-trying-build-090000069.html">https://ca.news.yahoo.com/dawson-city-residents-trying-build-090000069.html</a></p><p>The webcam animation from Thursday shows lots of steam in the cold weather, but apparently no real action in terms of ice formation.</p><div class="separator" style="clear: both; text-align: center;"><iframe allowfullscreen='allowfullscreen' webkitallowfullscreen='webkitallowfullscreen' mozallowfullscreen='mozallowfullscreen' width='320' height='266' src='https://www.blogger.com/video.g?token=AD6v5dxNXnYa6gclwniyiAkQm3PVsHYfAfw7PrOZBW7i8XA6br8EhRpG8sSWtTnmNFI9Q1jG8e1R_ZE4v_ZJce0LRw' class='b-hbp-video b-uploaded' frameborder='0'></iframe></div><br /><p><br /></p><p><br /></p>Richard Jameshttp://www.blogger.com/profile/08313902028896263276noreply@blogger.com0tag:blogger.com,1999:blog-4572286363399496963.post-58661645479467887352024-01-11T13:30:00.004-09:002024-01-11T13:35:31.314-09:00December Climate Data<p>Looking back at December, the dominant circulation feature near Alaska was a pronounced Bering Sea trough, with 500mb heights significantly below normal over western Alaska. And so it was another wet month for the state - the 8th wettest December on record (1925-present), according to NOAA/NCEI data. By my count, every month in 2023 except October was wetter than the long-term median for Alaska as a whole, and it was the wettest year statewide since... last year.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEimmQ9ujvJm0Zgx2irDYpuyv-iGocIiQ4UZsvs1mywPzlhnXVBmpG_Uk8TDZu8ZDTjA6sPdHBgubyWZVhTJnSHfBGXtqh82Sqa6IvmHrMHxxGvWvHJYsif1PLY9YNgmxqHsOCMfkSUCvy-bj63jQ0-yrEnPe2JiYf-J04nh5CeWxireENmDuNzaP-X8JhI/s787/z500.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="513" data-original-width="787" height="261" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEimmQ9ujvJm0Zgx2irDYpuyv-iGocIiQ4UZsvs1mywPzlhnXVBmpG_Uk8TDZu8ZDTjA6sPdHBgubyWZVhTJnSHfBGXtqh82Sqa6IvmHrMHxxGvWvHJYsif1PLY9YNgmxqHsOCMfkSUCvy-bj63jQ0-yrEnPe2JiYf-J04nh5CeWxireENmDuNzaP-X8JhI/w400-h261/z500.png" width="400" /></a></div><br /><p>December's mid-atmosphere flow pattern was quite reminiscent of a typical El Niño outcome. The map below shows the average 500mb height anomaly for 10 Decembers with strong El Niño conditions.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgDc54Ekpufv7XLq12Qum7hrxhhW4xzYjoRgG_i5mF4qS9HwjmM3RXP9p-aR7Hc-Jx9mdH7G5u-U2JeOzY6BiYVLZmwgJQ5B5KFNOKiz5JOAm5eNSRbHtGCpY_VJcaFHlnQcFt8t6pab5LxZR935vx7bNWoPsNFPPncSFJTOK387QptQyqGgZHIh-jr12M/s783/z500_dec_strong_elnino.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="492" data-original-width="783" height="251" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgDc54Ekpufv7XLq12Qum7hrxhhW4xzYjoRgG_i5mF4qS9HwjmM3RXP9p-aR7Hc-Jx9mdH7G5u-U2JeOzY6BiYVLZmwgJQ5B5KFNOKiz5JOAm5eNSRbHtGCpY_VJcaFHlnQcFt8t6pab5LxZR935vx7bNWoPsNFPPncSFJTOK387QptQyqGgZHIh-jr12M/w400-h251/z500_dec_strong_elnino.png" width="400" /></a></div><br /><p>Interestingly, this occurred despite dramatically different North Pacific SST patterns - compare the two maps below. This highlights the fact that it's tropical SSTs (and associated tropical convection) that tend to drive higher latitude circulation anomalies. Extratropical SSTs have an important influence in terms of setting a baseline for air temperatures locally and downstream, and they can reinforce prevailing weather patterns (e.g. a trough over locally colder ocean regions), but they can't compete with the likes of a strong El Niño in terms of overall circulation forcing.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhA4zvGbELC90bXBqgq2cWQBZjPnNv5bTAqGyQDTQSeYEvUh2imYDdbhcTbsNAsL_0kKsk8UMbVTzfjSxNQIJkpcp09mnEKhfRbzojpEvrOF9r3Ey-IlUWO4Ki6G2f0hAqj6NhVnGtokwWzdkGQ4J7IyVTPJ5K9jtHBz-mD3kN6V5WI20Q5Xr1I1AdOyZo/s788/sst.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="516" data-original-width="788" height="263" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhA4zvGbELC90bXBqgq2cWQBZjPnNv5bTAqGyQDTQSeYEvUh2imYDdbhcTbsNAsL_0kKsk8UMbVTzfjSxNQIJkpcp09mnEKhfRbzojpEvrOF9r3Ey-IlUWO4Ki6G2f0hAqj6NhVnGtokwWzdkGQ4J7IyVTPJ5K9jtHBz-mD3kN6V5WI20Q5Xr1I1AdOyZo/w400-h263/sst.png" width="400" /></a></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjYUD7PuWr3IlODdO8hhQs4tsq6zYvFU-CGl0Huqn9p0p97pqJiW6G2eGQzpehAFGfuud7l4klhldUTUQGdt1BpBEceWjGbpuPId-c-WZPTmn_882u1Os3Y_5hpmkUmtBwXvgd7z1momzaC0QTHvJwRLyg-rsy5ROlb9i4qrvld8PJp-1NT4gIQn91qOEc/s784/sst_dec_strong_elnino.png" style="margin-left: 1em; margin-right: 1em;"><br /><img border="0" data-original-height="492" data-original-width="784" height="251" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjYUD7PuWr3IlODdO8hhQs4tsq6zYvFU-CGl0Huqn9p0p97pqJiW6G2eGQzpehAFGfuud7l4klhldUTUQGdt1BpBEceWjGbpuPId-c-WZPTmn_882u1Os3Y_5hpmkUmtBwXvgd7z1momzaC0QTHvJwRLyg-rsy5ROlb9i4qrvld8PJp-1NT4gIQn91qOEc/w400-h251/sst_dec_strong_elnino.png" width="400" /></a></div><br /><p>Having noted El Niño's large-scale signature in the December circulation pattern, however, there were subtle differences. The Bering Sea trough was a bit farther north than usual, and that created less warm southerly flow and more cold westerly flow into western and southern Alaska. Compare the air temperature maps below; the southwestern quadrant of Alaska was colder than would be typical of El Niño.</p><div class="separator" style="clear: both; text-align: center;"><br /><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh8rYSxpxvmY6k1Lyr5RjCUPQMLku6B-I_6mKKJxakKe0tyy2zaPtIUSqApBARIt86SJr2XbW-dKJxac-ABBFaeu3QiN7M63ESmn8_l1Gb-76adZ9tpeYpm2AueogOOVgQ6DPmfG9n1yGgDcmXyGutArvtxskYB7Lb8x4VzkGYFoyO46ncpu2yELDR70Yo/s787/t2m.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="512" data-original-width="787" height="260" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh8rYSxpxvmY6k1Lyr5RjCUPQMLku6B-I_6mKKJxakKe0tyy2zaPtIUSqApBARIt86SJr2XbW-dKJxac-ABBFaeu3QiN7M63ESmn8_l1Gb-76adZ9tpeYpm2AueogOOVgQ6DPmfG9n1yGgDcmXyGutArvtxskYB7Lb8x4VzkGYFoyO46ncpu2yELDR70Yo/w400-h260/t2m.png" width="400" /></a></div><br /><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvasaayNDL2_k6v2SOeSGxCc8VwF57ggQKRgZJuL8rtsL8-ekH-_oQsvS1rXrNV6M2MHA1Sbot-bD38KCUPw36n5DjqEtTGm5sPCsLAJhmVBvHQBR0ylHaj2GpRRNDtJxbVfGB9_CYi4UuUnfUWRx4i69q1h0u8AWZY2Hup529HSWUtZ4fDZTzfNRyqAU/s785/t2m_dec_strong_elnino.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="490" data-original-width="785" height="250" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgvasaayNDL2_k6v2SOeSGxCc8VwF57ggQKRgZJuL8rtsL8-ekH-_oQsvS1rXrNV6M2MHA1Sbot-bD38KCUPw36n5DjqEtTGm5sPCsLAJhmVBvHQBR0ylHaj2GpRRNDtJxbVfGB9_CYi4UuUnfUWRx4i69q1h0u8AWZY2Hup529HSWUtZ4fDZTzfNRyqAU/w400-h250/t2m_dec_strong_elnino.png" width="400" /></a></div><br /><p>Here are my usual climate rank maps based on ERA5 and NOAA data:</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgWRqzdkAnJHj9kVvI-EgjZ0xYcJ0_oy2iDm-1-V2GrDDQXwBtVK79mwZCjKj14VJUuGdnHAbl_7j9B6oQQrsiwGVg9_uxuJfNzpvy9YFmqNZ_2f3ZZja6PEzBwvu6lbKHWyggU_zmFMfKkYssRzWFrJfwNtrSie3_92ZUAn4P2LoXf8XNEGgq-CNjPrOA/s770/akt2m_2023_12.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="770" height="311" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgWRqzdkAnJHj9kVvI-EgjZ0xYcJ0_oy2iDm-1-V2GrDDQXwBtVK79mwZCjKj14VJUuGdnHAbl_7j9B6oQQrsiwGVg9_uxuJfNzpvy9YFmqNZ_2f3ZZja6PEzBwvu6lbKHWyggU_zmFMfKkYssRzWFrJfwNtrSie3_92ZUAn4P2LoXf8XNEGgq-CNjPrOA/w400-h311/akt2m_2023_12.png" width="400" /></a></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiLXxzwyuvlL7FYK89vcNmwBmYDNZGSfgIFfa_kIyybfjzx2lUsA1-KEWAwTpsxDMl5jumzC1CygSfrdejldY6nbL4V5Z1fGs31nP8i6Cv4fLCYBAibmkXxIyHWsu7PRxuW1VtsNyUCe8xvujGMjniWiOf2b7MH3voRzDiPyTunkbpHvL7kVTo2KFndYN8/s770/aktmp_2023_12.png" style="margin-left: 1em; margin-right: 1em;"><br /><img border="0" data-original-height="600" data-original-width="770" height="311" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiLXxzwyuvlL7FYK89vcNmwBmYDNZGSfgIFfa_kIyybfjzx2lUsA1-KEWAwTpsxDMl5jumzC1CygSfrdejldY6nbL4V5Z1fGs31nP8i6Cv4fLCYBAibmkXxIyHWsu7PRxuW1VtsNyUCe8xvujGMjniWiOf2b7MH3voRzDiPyTunkbpHvL7kVTo2KFndYN8/w400-h311/aktmp_2023_12.png" width="400" /></a></div><br /><p>The Panhandle was exceptionally warm, with only a handful of Decembers being warmer in the modern climate history. The Southeast warmth was merely the western margin of a vast area of extreme warmth across Canada - the warmest December on record in many places. Canada is used to relatively warm winters during El Niño, but this was off the charts.</p><p>Here's the estimated distribution of precipitation anomalies: much wetter than normal in the Southeast and eastern interior, and either wet or dry elsewhere depending on which data source you prefer. Given the abysmal state of ground-truth precipitation measurements these days in Alaska, the ERA5 model data is probably preferable. </p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEig0Diapdg9ZF27sBOpwW8NC4ahQJVCWDaSE78hgcEQ5MfwFbRsqtMOSd3RfAiJOHVO_XwV40hMY-XclSlzMZcwkNpc73bOVqtpP68gkRrxt3J_S8DEfrqgNJfCUb5eitBODD7zc0nUUAEVAtUM11wIjNVrPFt19Ye7CySU5qqXFDIYDBXHAGkAgr6b6fk/s770/akpcp_2023_12.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="770" height="311" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEig0Diapdg9ZF27sBOpwW8NC4ahQJVCWDaSE78hgcEQ5MfwFbRsqtMOSd3RfAiJOHVO_XwV40hMY-XclSlzMZcwkNpc73bOVqtpP68gkRrxt3J_S8DEfrqgNJfCUb5eitBODD7zc0nUUAEVAtUM11wIjNVrPFt19Ye7CySU5qqXFDIYDBXHAGkAgr6b6fk/w400-h311/akpcp_2023_12.png" width="400" /></a></div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgjBgkwjuk6LzGAocKHg_pXeKsn_riew9wh8Ylnffu8gn6vEsmRId5C3vCU0Bqsq2aLSTLVgi-DxbFbJ8uqFxiznhmo6aQobtnW6atAbObhDvO-3HjWDOR2i85QjB6oVSQUovXqr4pPKKR4KxlQqjoR0iUPKK5129VhsDZ26z-jRyHnS2DJSzA_ZOILcZE/s770/akprcp_2023_12.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="770" height="311" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgjBgkwjuk6LzGAocKHg_pXeKsn_riew9wh8Ylnffu8gn6vEsmRId5C3vCU0Bqsq2aLSTLVgi-DxbFbJ8uqFxiznhmo6aQobtnW6atAbObhDvO-3HjWDOR2i85QjB6oVSQUovXqr4pPKKR4KxlQqjoR0iUPKK5129VhsDZ26z-jRyHnS2DJSzA_ZOILcZE/w400-h311/akprcp_2023_12.png" width="400" /></a></div><br /><div>Wind was below normal for a large part of the state, which is a bit surprising given the proximity of the trough; but it was evidently a rather stagnant pattern, with the storm track and higher winds taking aim at the Panhandle rather than running up into western Alaska.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjKGmxToqCocT_yZMAKhgl1eqF8-apoOicSh9J2Mm2zymRCjfYmK7QQj-iLthbOJMWG9KHfdj2bxhd4P8427r5ptTQGTGKFjtmJF0TW7VdYFKamWu4Q5OU-97Al5qLoiwVm2k1FBqjMTp29WVvcMFM9WVU9Pt-R58GYdL_5tfhm5YFH9dditB80q_WD1f8/s770/akwspd_2023_12.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="770" height="311" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjKGmxToqCocT_yZMAKhgl1eqF8-apoOicSh9J2Mm2zymRCjfYmK7QQj-iLthbOJMWG9KHfdj2bxhd4P8427r5ptTQGTGKFjtmJF0TW7VdYFKamWu4Q5OU-97Al5qLoiwVm2k1FBqjMTp29WVvcMFM9WVU9Pt-R58GYdL_5tfhm5YFH9dditB80q_WD1f8/w400-h311/akwspd_2023_12.png" width="400" /></a></div><br /><div><br /></div><div>As for the Arctic, warmth was extreme on the Canadian side. For 3 of the sites noted below - Resolute, Cambridge Bay, and Kugluktuk - it was the warmest December on record, and these all have more than 50 years of data. At Cambridge Bay, with 87 years of data, the previous December record was broken by more than 2°C (-20.1°C vs -22.2°C in 1987).</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiiN2WHbtT8aKkAnZO4I6Kr9cME-lE8G3qheFxukb6xkDQyC6kLL3WTdYphzlP8a9o4b6P3V6e0hyphenhyphen7eGuuah8ukcVIxG9JuwLWi1U5GEhcBlZCm7aikTwtmZ7fqDYCsue-dt9xTlNggq7TvKK3i21WaXMx8NTsAEOUKMJEuorghQYekDSHmhHjWkdY1iBc/s900/arcticanom_2023_12.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="669" data-original-width="900" height="297" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiiN2WHbtT8aKkAnZO4I6Kr9cME-lE8G3qheFxukb6xkDQyC6kLL3WTdYphzlP8a9o4b6P3V6e0hyphenhyphen7eGuuah8ukcVIxG9JuwLWi1U5GEhcBlZCm7aikTwtmZ7fqDYCsue-dt9xTlNggq7TvKK3i21WaXMx8NTsAEOUKMJEuorghQYekDSHmhHjWkdY1iBc/w400-h297/arcticanom_2023_12.png" width="400" /></a></div><br /><div>And as for Utqiaġvik, it was the 3rd warmest December on record, behind only 2017 and 2022.</div><div><br /></div><div>For more details, Rick Thoman's December summary is well worth a read:</div><div><br /></div><div><a href="https://alaskaclimate.substack.com/p/december-2023-alaska-climate-summary">https://alaskaclimate.substack.com/p/december-2023-alaska-climate-summary</a></div><div><br /></div>Richard Jameshttp://www.blogger.com/profile/08313902028896263276noreply@blogger.com1tag:blogger.com,1999:blog-4572286363399496963.post-11189509060542558082024-01-09T17:19:00.001-09:002024-01-09T17:19:48.238-09:00Follow-Up<p>A quick follow-up post on last week's big pressure gradient and associated wind: with ERA5 data now available, the peak MSLP difference between two Alaska land points was 95mb, i.e. not an all-time record, but certainly in the upper tier of these events.</p><p>However, I redid the historical calculation for land points from 170°W eastward, i.e. excluding the central and western Aleutians. The rationale is that last week's Aleutian cyclone was farther east than others that produced extreme pressure differences across the state, and I wanted to see if it might be an all-time record for the more restricted domain.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgC5TfedlFzzXEsHjO5pZknj04Ah_2OAUoTbBLcoQMBT-o4Hov4fHRvqZGJJhLRvll2Gh_qCTfoTKyMXY0suRS66VUtuXnNvTsGSfDpFn0mrzQs7xIUr7PvBEx43bvcysGSffyVvFpnTrj757uJoUSWubOInbSewTl6ftpWW6D2adnUVUH9RKjvlr8DvUA/s847/comphour.HOBoGFmcD1.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="655" data-original-width="847" height="309" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgC5TfedlFzzXEsHjO5pZknj04Ah_2OAUoTbBLcoQMBT-o4Hov4fHRvqZGJJhLRvll2Gh_qCTfoTKyMXY0suRS66VUtuXnNvTsGSfDpFn0mrzQs7xIUr7PvBEx43bvcysGSffyVvFpnTrj757uJoUSWubOInbSewTl6ftpWW6D2adnUVUH9RKjvlr8DvUA/w400-h309/comphour.HOBoGFmcD1.gif" width="400" /></a></div><br /><p>And the answer is - yes! The pressure difference of 95mb within Alaska east of 170°W is indeed the greatest back to 1950, based on hourly ERA5 data. Only two previous events exceeded 92mb across this domain: November 26, 1985, and December 5, 2009.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgNsFcv2dkPBVHVjnxnWeWX9GRinmV0EB6pUX6ubowqtNGaqftaIGNJGifvmwZ0NxNnu7AdKRPhqRAo9zuSS3PTVsKDLKcoJfF27HKBMN_GVVaa4WAJfo1CZ1zuB4UY9T-9TFz1xRNdZFTwe15_T5Jfb_MKqhkLKa9XzjIQbkXoob7yxT1BgZ4AFqcr744/s847/comphour.uNcA4sqynX.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="655" data-original-width="847" height="309" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgNsFcv2dkPBVHVjnxnWeWX9GRinmV0EB6pUX6ubowqtNGaqftaIGNJGifvmwZ0NxNnu7AdKRPhqRAo9zuSS3PTVsKDLKcoJfF27HKBMN_GVVaa4WAJfo1CZ1zuB4UY9T-9TFz1xRNdZFTwe15_T5Jfb_MKqhkLKa9XzjIQbkXoob7yxT1BgZ4AFqcr744/w400-h309/comphour.uNcA4sqynX.gif" width="400" /></a></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg4AnZGOJDVaYRhHeVOgNqQ1fmvaJw45sdZ8jVpAF8BNUm17E6zpskNbjIQKAQDS7jr3_rfHJw_so3otHnVtesSXR8K8Dfr1bE1ZIAcE6kh9JPAxcVAC0UT_n1Yc-BdvhaB-i96q_c9DUf4QaMoHZntVjHuyD5txQAHC6F3wpKwN8Uc1d4NFFu29DH1UPY/s847/comphour.mGz0KKo9e3.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="655" data-original-width="847" height="309" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg4AnZGOJDVaYRhHeVOgNqQ1fmvaJw45sdZ8jVpAF8BNUm17E6zpskNbjIQKAQDS7jr3_rfHJw_so3otHnVtesSXR8K8Dfr1bE1ZIAcE6kh9JPAxcVAC0UT_n1Yc-BdvhaB-i96q_c9DUf4QaMoHZntVjHuyD5txQAHC6F3wpKwN8Uc1d4NFFu29DH1UPY/w400-h309/comphour.mGz0KKo9e3.gif" width="400" /></a></div><br /><p>Here's a revised chart of the annual (cold season) maxima for the smaller domain:</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgkun3IywsdaMRaVHIBNraS3rqRH_ScXywkXO7Rfv3slNrXtGmtHJZdNXTSy6w84IMcjksiFbw3Jj8TbONjIgNV0llGiRq_R90WOdB258698RFKEvDd3u8NiY2AsYkmqYAtdUsu9tUvzDawvW43SSgimJ_fY1kTXJpqwmyrbiVKG3qjfSefaOrAsnXkmmE/s1941/mslp_range_across_alaska_lon170w.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1269" data-original-width="1941" height="261" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgkun3IywsdaMRaVHIBNraS3rqRH_ScXywkXO7Rfv3slNrXtGmtHJZdNXTSy6w84IMcjksiFbw3Jj8TbONjIgNV0llGiRq_R90WOdB258698RFKEvDd3u8NiY2AsYkmqYAtdUsu9tUvzDawvW43SSgimJ_fY1kTXJpqwmyrbiVKG3qjfSefaOrAsnXkmmE/w400-h261/mslp_range_across_alaska_lon170w.png" width="400" /></a></div><br /><p>Interestingly there seems to be a slight downward trend in the series, although it's not statistically significant. Another interesting aspect is the tendency for large positive outliers once every 10-20 years. Last week's set-up was a rare event.</p><p>Most regrettably, the high winds produced by this system led to treacherous conditions high on the Steese Highway last Wednesday, leading to the deaths of two motorists:</p><p><a href="https://www.adn.com/alaska-news/2024/01/05/recovery-of-2-found-dead-in-interior-alaska-vehicle-complicated-by-poor-weather-troopers-say/">https://www.adn.com/alaska-news/2024/01/05/recovery-of-2-found-dead-in-interior-alaska-vehicle-complicated-by-poor-weather-troopers-say/</a></p><p>Conditions were indeed very poor: here's the hourly data from the Eagle Summit SNOTEL site (click to enlarge). Columns are temperature and wind chill in °F, wind direction, wind speed in mph, and solar radiation (absolute and percent of possible).</p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiL1IZon48LgR7bjeT8pWD07QEJ1mrwWwzNEcPTFoUCYEGMax8cp96HdTkbGIQuAkypzlLSSamsFQxf4kiBPYgYEbwYri35_OmyFFIPBeKfkEedAaMizjHHToHZpkv9ptEq74XoupWxujQsFXxSqzJ0WxXG1XfewFOihZ6hmcAIOOuY0jBI_qRugnuO5xo/s709/eagle_summit.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="709" data-original-width="390" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiL1IZon48LgR7bjeT8pWD07QEJ1mrwWwzNEcPTFoUCYEGMax8cp96HdTkbGIQuAkypzlLSSamsFQxf4kiBPYgYEbwYri35_OmyFFIPBeKfkEedAaMizjHHToHZpkv9ptEq74XoupWxujQsFXxSqzJ0WxXG1XfewFOihZ6hmcAIOOuY0jBI_qRugnuO5xo/w220-h400/eagle_summit.png" width="220" /></a></div><br /><p>I don't have historical data for comparison, and Eagle Summit is notoriously cold and windy, but it's clearly not the kind of weather you want to encounter unprepared.</p><p><br /></p>Richard Jameshttp://www.blogger.com/profile/08313902028896263276noreply@blogger.com2tag:blogger.com,1999:blog-4572286363399496963.post-10089779459422339872024-01-04T06:10:00.000-09:002024-01-04T06:10:31.375-09:00Big Pressure GradientThere's been a very large pressure gradient across Alaska in the past couple of days, reflecting the contrast between Arctic high pressure to the northeast of Alaska and a very strong storm in the eastern Aleutians. As of yesterday morning, the difference in central pressure between these two features was 100mb, or about 10%.<div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgNkbClnztH48MY3J00Pkj3nZFT6bqyDRtySDSXF1d-pC_dwq4PlFJQe99w3x2kldFIPgxzzB3MBRLO2L4oaLz_7VNjiufyJk_EZvGAhTEZ7nFUrtTMecR5aBY3101I4u64qLO92xLXb-0quEoSuO4a9Fn1IMYjX1v4k_iH4HMZo5RjgswR1UNYang_38U/s1017/mslp.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="765" data-original-width="1017" height="301" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgNkbClnztH48MY3J00Pkj3nZFT6bqyDRtySDSXF1d-pC_dwq4PlFJQe99w3x2kldFIPgxzzB3MBRLO2L4oaLz_7VNjiufyJk_EZvGAhTEZ7nFUrtTMecR5aBY3101I4u64qLO92xLXb-0quEoSuO4a9Fn1IMYjX1v4k_iH4HMZo5RjgswR1UNYang_38U/w400-h301/mslp.png" width="400" /></a></div><br /><div><br /></div><div>Strong winds are the immediate result of big pressure differences, and so it's been very breezy in many places across Alaska; blizzard conditions have been occurring for the eastern Arctic coast.</div><div><br /></div><div>The 100mb pressure difference led me to wonder about the largest pressure difference ever measured across the state of Alaska. In the current event, the maximum pressure difference between two land points appears to have been around 90-95mb, judging from model MSLP maps - for example this one from Tuesday night (a range of 944mb to 1036mb).</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgqXP-oBC-oEshH0W-2v2JMSOTKhz_F1Y1GX0Ry-ZpsTbB8Sb8Nn-n2_Sg3j3_WqjSphBGkLtqiJsZEiKqKhGtrdJv80-NfWOpA7cQJJnHIGLlTcJd4VMTzSW6Uc3kOLO-8makqpgzAW4SasVDjHN8WjORUUCCLvgnbR8A4Fr15z447LKV7VbYZU1Tk8o8/s1024/ecmwf_mslp_pcpn_ak_2.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="809" data-original-width="1024" height="316" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgqXP-oBC-oEshH0W-2v2JMSOTKhz_F1Y1GX0Ry-ZpsTbB8Sb8Nn-n2_Sg3j3_WqjSphBGkLtqiJsZEiKqKhGtrdJv80-NfWOpA7cQJJnHIGLlTcJd4VMTzSW6Uc3kOLO-8makqpgzAW4SasVDjHN8WjORUUCCLvgnbR8A4Fr15z447LKV7VbYZU1Tk8o8/w400-h316/ecmwf_mslp_pcpn_ak_2.png" width="400" /></a></div><br /><div><div class="separator" style="clear: both; text-align: center;"><br /></div>Using hourly ERA5 reanalysis data back to 1950, I determined that the largest MSLP difference was 103mb, on February 4, 1989. This was a case with strong high pressure over the interior and southern Alaska (at the tail end of the notorious January 1989 cold spell, with record high MSLP), and only a modest cyclone over the Aleutians.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEisVEfvUyv49LKZfodZhGjS6AImFmvJiCR68nBaymFdxXbhLzg01rImVu6szBYzSj-F2kZ6oglgpJZkW2t0NhWHWTceBv1iZVWLkWdqLfdlPva7rdz7xSFXmNGsYSkfHl9Kiq7ODDWs8eDUe7RjpPWMlrRJ-pcrSTXKnyYa0fPH3e8sptGYb5pauywf5A0/s847/comphour.k08eAiJ1l9.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="655" data-original-width="847" height="309" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEisVEfvUyv49LKZfodZhGjS6AImFmvJiCR68nBaymFdxXbhLzg01rImVu6szBYzSj-F2kZ6oglgpJZkW2t0NhWHWTceBv1iZVWLkWdqLfdlPva7rdz7xSFXmNGsYSkfHl9Kiq7ODDWs8eDUe7RjpPWMlrRJ-pcrSTXKnyYa0fPH3e8sptGYb5pauywf5A0/w400-h309/comphour.k08eAiJ1l9.gif" width="400" /></a></div><br /><div>In contrast, just three years ago the MSLP difference across Alaska exceeded 100mb for only the second time since 1950, with an exceptionally strong western Aleutian cyclone being the culprit rather than a very strong anticyclone over the interior. This event also saw the lowest MSLP on record at an Alaskan land location, 923mb (according to ERA5 data since 1950).</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj5gEIJtGUua9P3S2F_lZuZUy8DqYqijgzWu111dKJxtuobuPjmQSlSQKV3EXMDgmIowXShgCabDlvXRFMjXYGD6W_ZK7lu3FfI0zKO7njRpYwLBHYyxqVpGF77xuoq4psHonYw_lH1omZQwbfzkbHAY1KdBop_y_d1-IkBiZ4iG3duap0NwIc5xJpaS_0/s847/comphour.SAbRJxu8vi.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="655" data-original-width="847" height="309" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj5gEIJtGUua9P3S2F_lZuZUy8DqYqijgzWu111dKJxtuobuPjmQSlSQKV3EXMDgmIowXShgCabDlvXRFMjXYGD6W_ZK7lu3FfI0zKO7njRpYwLBHYyxqVpGF77xuoq4psHonYw_lH1omZQwbfzkbHAY1KdBop_y_d1-IkBiZ4iG3duap0NwIc5xJpaS_0/w400-h309/comphour.SAbRJxu8vi.gif" width="400" /></a></div><br /><div>The time series of annual (winter) peak pressure differences shows no significant long-term trend. The peak pressure differences of each cold season have occurred in all months from November through April, with December being most common.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiDi2MkWufsirWJ3HRd7qcjIHE73_xcP7ulXogR9fsY5eZjLhZbZuN1bNWwVkrDwYL353S_J33sNE2y4h7VB_msDjDimIokXe5kUX-XXvGKbv5B6taO5E_Qt1ANKwP8VAWoNLweS7sAesDmDATCw2ByqA0Y8Mb8Sx4p5pentCk54sXuPf-Ycwa5b2A786c/s1949/mslp_range_across_alaska.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1218" data-original-width="1949" height="250" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiDi2MkWufsirWJ3HRd7qcjIHE73_xcP7ulXogR9fsY5eZjLhZbZuN1bNWwVkrDwYL353S_J33sNE2y4h7VB_msDjDimIokXe5kUX-XXvGKbv5B6taO5E_Qt1ANKwP8VAWoNLweS7sAesDmDATCw2ByqA0Y8Mb8Sx4p5pentCk54sXuPf-Ycwa5b2A786c/w400-h250/mslp_range_across_alaska.png" width="400" /></a></div><br /><div>There's also no significant overall relationship with El Niño/La Niña, although it's slightly intriguing that the strongest El Niño winters have tended not to produce a high pressure difference. The current event is therefore a bit unusual in this regard, because we certainly have a strong El Niño in play at the moment.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh2f0Ovm4IX1v8YhXkI23K-yiwzfT2HZ6sgcIJv0uZBWdHkJLFvogI_zjfSsK2-pDo6Qv7n9Isq9-_w760ACXOoWUuyIA1W41jvxAgiNWuCsEGlpKXytbHS4FtrpPzbnOCA82wS37oCbypp975E0xrLeaN88j8_pXsRiFBgeirIfrSnFhbv58pdGqR3C00/s2017/mslp_range_across_alaska_vs_oni.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1257" data-original-width="2017" height="249" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh2f0Ovm4IX1v8YhXkI23K-yiwzfT2HZ6sgcIJv0uZBWdHkJLFvogI_zjfSsK2-pDo6Qv7n9Isq9-_w760ACXOoWUuyIA1W41jvxAgiNWuCsEGlpKXytbHS4FtrpPzbnOCA82wS37oCbypp975E0xrLeaN88j8_pXsRiFBgeirIfrSnFhbv58pdGqR3C00/w400-h249/mslp_range_across_alaska_vs_oni.png" width="400" /></a></div><br /><div>I'll provide an update with the ERA5 peak MSLP difference for the current event when the data is released in a few days' time.</div><div><br /></div>Richard Jameshttp://www.blogger.com/profile/08313902028896263276noreply@blogger.com5tag:blogger.com,1999:blog-4572286363399496963.post-84117193628422660762023-12-27T08:39:00.001-09:002023-12-27T08:39:59.991-09:00Cold At LastCold air aloft and clear skies allowed temperatures to drop to the coldest of the season so far across much of western Alaska in the past couple of days, and -40° was breached for the first time at a measuring location in the state. This is much later than usual. Several sites dropped below -35°F earlier in the month, including -39°F at the Ruby 44 ESE co-op site, but yesterday's cold was more significant. Here are some 24-hour low temperatures ending at midnight last night.<div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiCGkUtanoGGlpo17tkNKacmO8Okn7GG8M9MQWH6s5qQR77Bh_-hJPY5muh-j066sdGOKF20FIv8Itv2XsrrD2keCbT_pVb4eM9S1kFcppgrFtyMSL56cn6pWiaUrLMHdXknPD3OBBXS1_2CfrpcaXf7JsX5Mw-RRHIIKKMWdi5gTfmFNkvu_NX_h0AjPw/s1337/tmin_20231226.jpg" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="848" data-original-width="1337" height="254" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiCGkUtanoGGlpo17tkNKacmO8Okn7GG8M9MQWH6s5qQR77Bh_-hJPY5muh-j066sdGOKF20FIv8Itv2XsrrD2keCbT_pVb4eM9S1kFcppgrFtyMSL56cn6pWiaUrLMHdXknPD3OBBXS1_2CfrpcaXf7JsX5Mw-RRHIIKKMWdi5gTfmFNkvu_NX_h0AjPw/w400-h254/tmin_20231226.jpg" width="400" /></a></div><br /><div>The coldest reported (not on the map) was -49°F at the Kaiyuh RAWS near Kaltag. McGrath reached -45°F, the coldest since the pre-Christmas cold spell of last year.</div><div><br /></div><div>But more unusually, Bethel reached -30°F, the coldest since February 2017.</div><div><br /></div><div>In other news, Anchorage snowfall continues to track at record levels, with 79" so far this season. This is above the normal total for the entire winter.</div><div><br /></div><div>On a different note, while fiddling with climate data over the break, I took a look at the relationship between temperatures aloft and temperatures at the surface in the depths of winter, for all the major balloon sounding sites in Alaska. For temperatures "aloft" I used the 850mb pressure level, which averages about 4000-4500 feet above sea level at this time of year.</div><div><br /></div><div>There's a robust positive correlation, of course, between 850mb and surface temperatures at all locations, but it does vary quite a bit across the state. The site with the highest correlation of average December-January temperatures is Nome:</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiFVN0125UEWp-jwoVCIBdnsVb5t7-olpegKVlI_tXow0mSuACHUUMO5ot8GfcIFlCI29d2AGbvImE5sSDIx5SeFKHBhts-Sw2Ujcc68lZSadfMyni18nDcpLbCNJoC8bwpevqiGWT_sB5whuF2Kwv6vzUxj6qVgs94QPu_diJsOVowiQlhSbVNfel3ZRI/s1970/tsfc_vs_t850_paom.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1148" data-original-width="1970" height="233" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiFVN0125UEWp-jwoVCIBdnsVb5t7-olpegKVlI_tXow0mSuACHUUMO5ot8GfcIFlCI29d2AGbvImE5sSDIx5SeFKHBhts-Sw2Ujcc68lZSadfMyni18nDcpLbCNJoC8bwpevqiGWT_sB5whuF2Kwv6vzUxj6qVgs94QPu_diJsOVowiQlhSbVNfel3ZRI/w400-h233/tsfc_vs_t850_paom.png" width="400" /></a></div><br /><div><br /></div><div>The lowest correlation is at Utqiaġvik, but this is at least partly because of the differing trends at the surface and aloft: surface temperatures have warmed more rapidly because of sea ice loss.</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgI4QdmCIiQS66klR9CN65A4L5nbT_sqQiadKMNWnyRlrk7XuNaWYXinMnRDnPw17v0hcvQ6ogecOFZIJ2Z2Ie6OJKJQYsyXaMjRuZBhnYx_sLEgR0aszL3-v6dm-rk3fSslOhcMUKEdrPhqF1DotDEuLqcCc88AQFc4kLup6ULdxv_4c19TzMhyQjdvVY/s1980/tsfc_vs_t850_pabr.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1143" data-original-width="1980" height="231" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgI4QdmCIiQS66klR9CN65A4L5nbT_sqQiadKMNWnyRlrk7XuNaWYXinMnRDnPw17v0hcvQ6ogecOFZIJ2Z2Ie6OJKJQYsyXaMjRuZBhnYx_sLEgR0aszL3-v6dm-rk3fSslOhcMUKEdrPhqF1DotDEuLqcCc88AQFc4kLup6ULdxv_4c19TzMhyQjdvVY/w400-h231/tsfc_vs_t850_pabr.png" width="400" /></a></div><br /><div><br /></div><div>In general we expect lower correlations for more interior locations that have strong and near-permanent surface-based temperature inversions at this time of year, and higher correlations at maritime sites where inversions are less common. This is broadly what we find:</div><div><br /></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEintqV2j6lBI-qcciBYiNpItZdZgkbeOiC1TxParGAYJTDvGsE7qPXPCHNXiIO0e_ESnyUOIhS2mjgPyxdeBhux4wE77ls8txPDVYVqHR_oJtRsm41bzQzVLL0LwbBUDO-IqRiadYZ_PiU6lQHhmbhTBEVGszvEjyZUOlhuq5uEOMoC9oQQRuQGXhGJGEg/s1734/tsfc_vs_t850.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="1255" data-original-width="1734" height="290" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEintqV2j6lBI-qcciBYiNpItZdZgkbeOiC1TxParGAYJTDvGsE7qPXPCHNXiIO0e_ESnyUOIhS2mjgPyxdeBhux4wE77ls8txPDVYVqHR_oJtRsm41bzQzVLL0LwbBUDO-IqRiadYZ_PiU6lQHhmbhTBEVGszvEjyZUOlhuq5uEOMoC9oQQRuQGXhGJGEg/w400-h290/tsfc_vs_t850.png" width="400" /></a></div><br /><div>The highly maritime climates of Kodiak, Cold Bay, and St Paul Island are at the top right, with Annette Island also quite similar. On the far left, with strong inversions, are Fairbanks and McGrath, and these sites have a weaker relationship between surface and 850mb temperatures. Anchorage is right in the middle.</div><div><br /></div><div>The only one that surprises me is Yakutat, with a weak correlation despite a rather maritime climate and positive lapse rate (i.e. no temperature inversion on average). More investigation would be needed to illustrate why this is the case.</div><div><br /></div>Richard Jameshttp://www.blogger.com/profile/08313902028896263276noreply@blogger.com5tag:blogger.com,1999:blog-4572286363399496963.post-92011806202736136512023-12-20T12:39:00.003-09:002023-12-20T12:39:57.476-09:00AI Forecast Follow-Up<p>Last month I penned a few comments on the big news in the weather industry: the emergence of AI models as a legitimate competitor to traditional physics-based models for weather forecasting.</p><p>To provide a more concrete example of the impressive performance of the new models, I pulled out forecasts for Fairbanks from two of the AI models that I've been running over the past couple of months. Note how remarkable this is: the models can be run on pretty modest hardware; you don't need a supercomputer.</p><p>Here's a basic comparison of forecast skill for days 1-14 of the 2m temperature forecasts for Fairbanks (click to enlarge). Here I'm using ERA5 reanalysis data as "ground truth".</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiuRBP64J9rhBfyKzIGWlDs-kPBVjVIOazR-CmoEc68T1pexaw9hM58gpkta_9r_UeKHKJAVNhrcZk-OGwfIfXQyW95anF_nuZhywHNRFsbLD8s_CyaOeYDjD5jgTkEGOE3Gj_7ay7rwNhkavi4Y-ltRSb_NJVPONS24ZcvdBClX1mlJxYhqBXotDzzzzM/s1053/ai_model_skill_t2m.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="616" data-original-width="1053" height="234" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiuRBP64J9rhBfyKzIGWlDs-kPBVjVIOazR-CmoEc68T1pexaw9hM58gpkta_9r_UeKHKJAVNhrcZk-OGwfIfXQyW95anF_nuZhywHNRFsbLD8s_CyaOeYDjD5jgTkEGOE3Gj_7ay7rwNhkavi4Y-ltRSb_NJVPONS24ZcvdBClX1mlJxYhqBXotDzzzzM/w400-h234/ai_model_skill_t2m.png" width="400" /></a></div><br /><p>The two AI models are GraphCast (Google) and FourCastNet (NVIDIA), and I'm running FourCastNet with 50 members based on the initial conditions in the ECMWF ensemble forecast. GraphCast is more computationally demanding, so I only have a single member each day. The usual (traditional) ECMWF and GEFS ensembles have 51 and 31 members respectively.</p><p>Remarkably, GraphCast's single forecast member equals the ECMWF ensemble skill out to 9 days. The ECMWF ensemble is the gold standard for medium-range forecasting, so this is a terrific result that confirms the power of the new models. In contrast, FourCastNet starts out strong but roughly equals GEFS after 5 days, with inferior skill. Note that systematic bias could affect these results to some extent, as I used the ERA5 seasonal normal as the baseline, without any bias correction.</p><p>Looking at the mid-atmosphere 500mb height forecasts, it's interesting to note that GraphCast drops off significantly after 10 days, while FourCastNet shows a very strong performance. This may be reflecting the benefit of an ensemble approach for the medium-range (7-14 day) forecast.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj-RNXPARIgi2QTjGuFKC4SCDIzhJk_A-_yEt9yd9UK2B7Q5fZ-pSePJOMiZDfl3A0iPNYWm47ZdjrXflpOAOKAOe9XnJICAxoUZWPBIUFrMxjVqLqSZwLjcTjxDOmkIun6gwJcCDCWj976-J6eiiM3PLXVdTM7uNJxDDm1W6BWpf5BhcOoBeTJeyjclfA/s1055/ai_model_skill_z500.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="619" data-original-width="1055" height="235" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj-RNXPARIgi2QTjGuFKC4SCDIzhJk_A-_yEt9yd9UK2B7Q5fZ-pSePJOMiZDfl3A0iPNYWm47ZdjrXflpOAOKAOe9XnJICAxoUZWPBIUFrMxjVqLqSZwLjcTjxDOmkIun6gwJcCDCWj976-J6eiiM3PLXVdTM7uNJxDDm1W6BWpf5BhcOoBeTJeyjclfA/w400-h235/ai_model_skill_z500.png" width="400" /></a></div><br /><p>More results will be forthcoming when I have time. In the meantime, here's the latest forecast I have access to: the message is "warmer than normal" in Fairbanks, and perhaps especially around Christmas Eve and New Year's Eve.</p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgISRoiMM4Sq09UtIeNWm1Tw7CabEBTMRVkkPH99LyytIrPbKTS7f7dIvsHTMzqNle3R9ozDUifDFrKLslBelkcepN5lCe0PiYPwYcBxxNvb9PIpGMLkeHhiU2BL0sGcrETkyJU7-GC9B9snC8UJaBqj6rS0uivT7e8aTDO37VG6nS49hORgGbXMHtbpjY/s770/t2m_2023121900_PAFA.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="600" data-original-width="770" height="249" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgISRoiMM4Sq09UtIeNWm1Tw7CabEBTMRVkkPH99LyytIrPbKTS7f7dIvsHTMzqNle3R9ozDUifDFrKLslBelkcepN5lCe0PiYPwYcBxxNvb9PIpGMLkeHhiU2BL0sGcrETkyJU7-GC9B9snC8UJaBqj6rS0uivT7e8aTDO37VG6nS49hORgGbXMHtbpjY/s320/t2m_2023121900_PAFA.png" width="320" /></a></div><br /><p>The CPC's 8-14 day forecast also calls for warmth for central and eastern Alaska around the New Year period. It's a very typical El Niño pattern nationwide.</p><p><br /></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgP-DqDbcn5Vjw_YvD5BZ226lNnKJjhu9Rf6rJOfSCTJ5tkPaXoDzgxfOX4U6x3A-kCTcu8NcQJXjKY5WIMsevu9x3sf-F_8BYZeEr9l5ttuyeNeFFpYPoKvaD7Im4tDj_vLy5CF1r8w-ladw4pEJLgrv_fyl8U3e3FYySrfh1iXbyHG_QR8ILQ5OlAZ-s/s3300/814temp.new.gif" style="margin-left: 1em; margin-right: 1em;"><img border="0" data-original-height="2550" data-original-width="3300" height="309" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgP-DqDbcn5Vjw_YvD5BZ226lNnKJjhu9Rf6rJOfSCTJ5tkPaXoDzgxfOX4U6x3A-kCTcu8NcQJXjKY5WIMsevu9x3sf-F_8BYZeEr9l5ttuyeNeFFpYPoKvaD7Im4tDj_vLy5CF1r8w-ladw4pEJLgrv_fyl8U3e3FYySrfh1iXbyHG_QR8ILQ5OlAZ-s/w400-h309/814temp.new.gif" width="400" /></a></div><br /><p><br /></p>Richard Jameshttp://www.blogger.com/profile/08313902028896263276noreply@blogger.com3