Wednesday, February 10, 2021

Arctic High Pressure

Harsh cold is persisting at many interior locations and also across the Brooks Range and North Slope, with numerous -40°F to -50°F readings this morning, and some even colder.  Notable low temperatures in the past couple of days include:

-49°F at Galena in the western interior

-56°F at the Birch Creek RAWS just above the Yukon Flats

-46°F at Anaktuvuk Pass, 2100' elevation in the Brooks Range

-58°F on the upper Sagavanirktok River

The latter is apparently the coldest observed in Alaska so far this winter; Chicken reached -57°F a couple of days ago.

Severe wind chill continues to afflict Arctic coastal sites, and the breeze even picked up at Umiat today: around 6am, a mean hourly wind speed of 11 mph combined with a temperature of -52°F.  This turns out to be the highest wind speed on record at Umiat with a temperature below -50°F (with hourly data back to 2007).

Looking at the surface analysis from 3pm yesterday, we see the same Arctic high pressure system that I highlighted in my last two posts - except now the high has expanded over an enormous area from the Chukchi Sea to northwestern Canada and across to Greenland.  It's really a sight to behold: click to enlarge.

The all-time record highest MSLP over the Arctic Ocean is 1069mb (per ERA5 data since 1950), so this is not far off.  It's a rare anomaly, and it's responsible not just for the cold in Alaska, but for outbreaks of severe cold far to the south in the lower 48 and also in Europe.

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