February Climate Data

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.

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:

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.

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.

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).

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:

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.

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:

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.

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.

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.