Follow-Up

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.

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.

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.

Here's a revised chart of the annual (cold season) maxima for the smaller domain:

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.

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:

https://www.adn.com/alaska-news/2024/01/05/recovery-of-2-found-dead-in-interior-alaska-vehicle-complicated-by-poor-weather-troopers-say/

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).

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.