Saturday, February 8, 2020

North Slope Cold

Just a quick update this evening to note an episode of extremely low wind chill on the North Slope owing to frigid temperatures combined with breezy conditions.  This is a combination that would be almost unheard of in Alaska's interior, where severe cold (say -50°F or below) develops only when winds are calm.

The lowest wind chill value I've seen was at Nuiqsut, just south of the Colville River delta: yesterday evening it was -52°F with a 10 knot sustained wind, which is good for a -82°F wind chill index.  This morning was even colder (as low as -55°F) but with a slightly lighter breeze.  The only colder time in the 20-year history of data from Nuiqsut was in early 2012, when the air temperature reached -62°F (Jan 24) and the wind chill touched -86°F (Jan 31).

Deadhorse also saw its second worst wind chill episode last night, reaching -80°F (rounded) with an air temperature of -47°F.  Only late January 2012 was colder  (-51°F, wind chill -85°F).

Other sites with wind chills in the same vicinity were Kuparuk (-80°F) and the notorious (but well inland) cold spot of Umiat (air temperature -55°F, wind chill -79°F).

It's interesting to note that Deadhorse has seen an average wind chill of -47°F so far this year, and this is second only to 1989 (-48°F); mostly complete hourly data extends back to the early 1980s.  Of course January 1989 was an extremely cold month in Alaska, and like this year, 1989 also saw a very strong polar vortex with lower than normal MSLP in much of the Arctic basin (strongly positive AO phase). 

Compare the MSLP maps for January 1989 and 2020 below.  While they're not identical, the north-south pressure gradient across Alaska is very similar.  Of course below-normal MSLP in the high Arctic would tend to favor stronger than normal offshore (and therefore cold) winds along Alaska's north coast, and so it makes sense that wind chills were also severe in 1989.

1 comment:

  1. The Polar Vortex is circling the wagons for another two week cold event. It'll be informative after it's finally done as to what's the drivers.