Long-Duration Blizzard

Alaska's Arctic coastline has been suffering high winds and blowing snow for most of this week, and although the peak wind speeds haven't been extreme, the duration of the wind storm is notable.  Looking at data from Utqiaġvik, Deadhorse, and Barter Island, all three sites have seen daily mean wind speeds above 20 knots (23 mph) on each of the last 5 days, with gusts exceeding 40mph at times.  The charts below show wind data from these 3 sites respectively (Utqiaġvik top, Deadhorse middle, Barter Island bottom - click to enlarge):

Using consecutive days above 20 knots as a threshold, the last time these sites saw a blow of this duration was November 2023 at Deadhorse and Barter Island, and December 2017 in Utqiaġvik - although there have been some other events more recently with nearly the same wind speed.

Several months ago, reader Mike asked whether El Niño affects the frequency and strength of North Slope blizzards.  I've been meaning to look into this, and I'll write up some comments soon, but preliminary results from ERA5 reanalysis data suggest the following:

(1) El Niño (and its counterpart La Niña) produce little or no change in frequency, strength, or duration of high winds in winter along the Arctic coast.  However,

(2) the direction of high winds is affected.  El Niño winters produce more blizzards from an easterly direction, but during La Niña there is an increased frequency of westerly storms.  The current wind storm is easterly, consistent with the ongoing (record-strong) El Niño event.

The directional effect makes sense, because El Niño reliably produces lower than normal pressure from the Bering Sea to the Gulf of Alaska, and that increases the easterly component of flow to the north over Alaska, including the North Slope.  With low pressure hanging out in the south, it's easier than normal to generate a south-to-north pressure gradient when high pressure sets up over the Arctic Ocean.  This morning's MSLP analysis is a good example: observe the 1038mb high over the high Arctic and the 972mb low in the Gulf of Alaska.

The MSLP anomaly for a 7-day period ending on Monday also depicts the same pattern: this is a recipe for strong easterly flow across Alaska's Arctic coastline.

More to come in a subsequent discussion.