Saturday, February 5, 2022

Norton Sound Wind Storm

One month ago, I posted about a long-duration wind storm in south-central Alaska, and this week it was the turn of Norton Sound communities to endure sustained high winds - and in particular, Unalakleet.  Rick Thoman highlighted this on Twitter and in the following article:

Here's Rick's graphic showing hourly wind speeds in Unalakleet.  Sustained wind speeds were 50mph or higher most of the time from Wednesday morning through late Thursday afternoon, with gusts exceeding 70mph at the height of the event. 

Wind speed measurements have been made in Unalakleet, in one form or another, most of the time back to 1948.  Looking at that data, Wednesday and Thursday were the 2nd and 3rd most windy days on record in Unalakleet, with the only windier day (midnight-to-midnight) being January 21, 1952.  (This is taking the wind data at face value, although we know measurement techniques have changed a lot.)

This week is also the only time on record when the daily average wind speed was above 40mph for 3 consecutive days - and this is quite remarkable, given that Unalakleet is certainly a windy place in winter.

Tuesday through Thursday this week also had the highest 3-day average wind speed on record (based on midnight-to-midnight daily values).  Here are the winter peak values back to 1950-51.  The variability from year to year is generally quite small, so this event is a huge outlier: 5.5 standard deviations from the mean of the last 30 years!

The MSLP maps below (courtesy of Environment Canada) show the near-stationary weather pattern that gave rise to this extreme event.  Note the persistence of the tight pressure gradient over western Alaska, with the flow being squeezed between a stubborn anticyclone over Arctic Alaska and deep low pressure over the Aleutians.

3am AKST Tuesday:

3am AKST Wednesday:

3am AKST Thursday:

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