Thunderstorms over the Chukchi Sea and Beaufort Sea north of Alaska

July 12th, 2021 |

Suomi NPP VIIRS Infrared Window (11.45 µm) and Visible (0.64 µm) images [click to play animation | MP4]

Suomi NPP VIIRS Infrared Window (11.45 µm) and Visible (0.64 µm) images [click to play animation | MP4]

A sequence of Suomi NPP VIIRS Infrared Window (11.45 µm) and Visible (0.64 µm) images (above) showed snapshots of thunderstorms over parts of the Chukchi Sea and the Beaufort Sea off the northern coast of Alaska on 12 July 2021. The coldest convective cloud-top infrared brightness temperatures were in the -30 to -40ºC range. Unusual aspects of these thunderstorms included their high latitude location over ice-covered waters — as far north as 75ºN latitude — and the large amount of cloud-to-surface lightning strikes that they produced.



These thunderstorms were not surface-based — instead, they were forced by an approaching cold front (surface analyses) which helped to release elevated instability within the 500-300 hPa layer (below).

Suomi NPP VIIRS Infrared Window (11.45 µm) images, with contours of NAM40 lapse rate within the 500-300 hPa layer [click to enlarge]

Suomi NPP VIIRS Infrared Window (11.45 µm) images, with contours of NAM40 lapse rate within the 500-300 hPa layer [click to enlarge]

Rawnsonde data from Utqiagvik (PABR) were not available (due to ongoing equipment malfunction at that site) — but a NUCAPS profile near the southernmost cluster of convection around 15 UTC (below) showed the layer of instability aloft.

NUCAPS profile near thunderstorms off the northern coast of Alaska [click to enlarge]

NUCAPS profile near thunderstorms off the northern coast of Alaska [click to enlarge]