The first -40º temperature of the winter in Alaska

November 24th, 2018 |

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

A sequence of Suomi NPP VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images centered over the North Slope of Alaska (above) showed a few patches of thin stratus cloud drifting westward on 24 November 2018. Ample illumination from the Moon — which was in the Waning Gibbous phase, at 98% of Full — maximized the “visible image at night” capability of the Day/Night Band. A faster animation of Infrared images helped to emphasize the westward motion of multi-year drift ice in the Beaufort Sea as it collided with the growing wedge of first-year land-fast ice off the northeast coast of Alaska.

In areas with deeper snow cover that remained generally cloud-free for long periods of time, temperatures at first-order stations dropped into the -20s and -30s F; a low of -35ºF was recorded at Nuiqsut (PAQT). A closer look at the 2314 UTC Infrared image (below) revealed surface brightness temperatures as cold as -47ºC or -53ºF (lighter shades of yellow) in the valleys near Galbraith Lake (PAGB).

Suomi NPP VIIRS Infrared Window (11.45 µm) image at 2314 UTC [click to enlarge]

Suomi NPP VIIRS Infrared Window (11.45 µm) image at 2314 UTC [click to enlarge]

The RAWS site at Umiat Airfield (PAUM) registered a minimum temperature of -40ºF (hourly summary) at 2123 UTC on 24 November (below) — this was the first reliable -40º temperature of the 2018/2019 Winter season in Alaska. Farther to the east, the HADS site at Sagavanirktok recorded a low of -44F, but that max/min temperature data was flagged as being suspect (red) by Mesowest quality control.

Minimum and maximum temperatures for the 24-hour period ending at 20 UTC on 25 November [click to enlarge]

Minimum and maximum temperatures for the 24-hour period ending at 20 UTC on 25 November [click to enlarge]