Monday, November 27, 2023
Tuesday, November 21, 2023
Weather is never very far from the news in a place as big as Alaska, and the more extreme events aren't usually good news. Yesterday a major Gulf of Alaska storm barreled into a cold air mass and high pressure over southern Alaska, and the results were dramatic: damaging winds in the Matanuska Valley, and a major landslide down south in Wrangell. Sadly the landslide brought loss of life, and perhaps worse than the 2020 Haines landslide.
ADN news links:
The rain in the Southeast doesn't appear to have been particularly unusual for the region; the map below shows 72-hour totals (click to enlarge). But it was pretty wet earlier in the autumn, so there may have been a compounding risk. Sitka is in the top 10 for rainfall since September 1.
As for the winds around Palmer and Wasilla, the map below shows how localized the wind storm was in the greater Anchorage area (showing yesterday's peak gusts in mph).
Thursday, November 16, 2023
A few comments on various topics. First, the snow onslaught in Anchorage: the recent 10-day total of 38" amounts to the 3rd highest on record. Last year's December snow was even a bit greater, and the top event was back in February 1996.
It's really remarkable to see such a large amount of snow at the airport - where there is typically less snow than across most of the area - and in back-to-back years. With La Niña last winter and El Niño this winter, we can't pin the blame on similar climate forcing, so perhaps it's just "luck of the draw".
Second, the Tanana River at Nenana froze up last week on Wednesday the 8th. The scene is suitably wintry today:
But the mighty Yukon River hasn't frozen over at Dawson yet; here's the latest video from the webcam:
The situation at Dawson looks about the same as last year at this time:
Long-time readers will recall discussion of the lack of a proper freeze-up all winter long at Dawson in some recent years:
This autumn has certainly been on the warm side of normal in Dawson, but it's not breaking records for lack of freezing potential: here's a chart of accumulated freezing degree days (accumulated temperature differential below 32°F):
This is from the reliably-reporting "LRP" site in Dawson, not the airport, where many observations are missing. The city does have a much longer history of climate observations, of course, but it seems there are some discrepancies between the different climate sites that would affect any long-term trend analysis.
And finally, I'll highlight the remarkable lack of sea ice along Alaska's west coast at this time, related to persistent southerly winds and warmth. Rick Thoman posted a graphic to illustrate:
"Sea ice concentration analysis for Wednesday and the same date last year from the National Weather Service Alaska Region Sea Ice Program. Much less ice in the southern Chukchi and Bering Seas currently than this date last year. November 15 and effectively no ice in Kotzebue Sound is especially shocking, even by recent norms."
Here's a longer archive of November 15 analyses, from 2021 (top) to 2018 (bottom):
Friday, November 10, 2023
Tuesday, November 7, 2023
Rick Thoman has a nice write-up of October's Arctic and Alaska climate anomalies here:
The precipitation contrasts across Alaska were striking: it was much drier than normal for the time of year in the southwest and south-central, but the North Slope and eastern Alaska were notably damp. Rick notes that the Utqiaġvik CRN site measured 1.68" of liquid-equivalent for the month - the highest on record there for October (at either the CRN site or the much longer Barrow/Utqiaġvik climate site). It's also the fourth consecutive month with more than an inch of precipitation at the CRN location.
Snowfall was also relatively abundant in eastern Alaska: as high as 19" in Tok and 17" in Eagle. Also 18" on Keystone Ridge outside of Fairbanks.
Here's a look at snow water on the ground at 5-day intervals through the month, expressed in terms of historical percentile, and estimated by the ERA5 model:
The snowpack was established on October 6 in Fairbanks (considerably earlier than normal), but very little snow remained by the end of the month in the southwestern quadrant of the state. The last week of the month was very mild, but chilly weather earlier in the month allowed for a near-normal monthly average temperature for much of the interior. The Aleutians, North Slope, and Southeast were notably warmer than normal, however.
As for wind, October was relatively calm for the southwest and south-central, but windier than normal in the north and northeast.
Here's the mid-atmosphere pressure pattern that contributed to the surface climate anomalies: the ridge over southwestern Alaska explains the dry and calm weather there.
Sea surface temperatures remain much higher than normal in the western Bering Sea and northwestern North Pacific, so we can expect that winds from that direction will tend to bring unusually mild conditions to Alaska in the coming months.
Given that we have a strong El Niño in play this winter, which tends to produce a strong Aleutian low and frequent southwesterly flow across Alaska, I'd say the chances of a very mild winter are much higher than normal. NOAA's Climate Prediction Center agrees:
For a comprehensive discussion of the winter outlook, check out Rick Thoman's November 17 presentation here:
Wednesday, November 1, 2023
After relatively cool conditions for much of autumn in Alaska as a whole, the last week of October brought a change to unusual warmth. Blame a big ridge extending north from the Gulf of Alaska, allowing warm air to be transported northward into the western part of the state and up to the Arctic. Here are the average 500mb height and 850mb winds for the week ending October 30:
And the resulting 850mb temperature departure from normal:
Warmth in Alaska's far north has been an oft-repeated theme in the past two decades, and this year Utqiaġvik ended up with a top-5 warm October, although it wasn't as extreme as 2016 and 2019. Here's the now (I trust) well-known chart of October temperatures there, showing the profound change in the local climate from loss of October sea ice.
For the state as a whole, October 30th was the warmest day of the month in comparison to normal. The figure below shows the widespread distribution of unusual warmth, with the statewide average climbing into the 95th percentile for the time of year. The standardized anomaly numbers reflect my calculations that account for seasonal skewness, as discussed recently here.