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Hurricane Force low moves into the Bering Sea

By Scott Bachmeier •

GOES-17 Air Mass RGB and Mid-level Water Vapor (6.9 µm) images [click to play animation | MP4]

GOES-17 Air Mass RGB and Mid-level Water Vapor (6.9 µm) images [click to play animation | MP4]

GOES-17 (GOES-West) Air Mass RGB and Mid-level Water Vapor (6.9 µm) images (above) showed an anomalously-deep Hurricane Force low pressure system as it approached the western Aleutian Islands and moved into the Bering Sea on 31 December 2020 (surface analyses). The peak wind gust at Shemya (PASY) was 72 knots (83 mph) at 09 UTC.

A closer view using a GOES-17 Water Vapor image at 0910 UTC (below) included plots of Metop ASCAT surface scatterometer winds — the highest ASCAT wind speeds were 66 knots north of the storm center, and 78 knots south of the storm center.

GOES-17 Mid-level Water Vapor (6.9 µm) image at 0910 UTC, with plots of Metop ASCAT surface scatterometer winds [click to enlarge]

GOES-17 Mid-level Water Vapor (6.9 µm) image at 0910 UTC, with plots of Metop ASCAT surface scatterometer winds [click to enlarge]

A toggle between Suomi NPP VIIRS Infrared Window (11.45 µm) and Day/Night Band (0.7 µm) images (below) showed the cloud circulation associated with the low at 1457 UTC — ample illumination from a Full Moon provided a superb visible image at night.

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

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

In another comparison of Suomi NPP VIIRS Infrared Window and Day/Night Band images about 10 hours later at 0053 UTC on 01 January (below), note the ship report approximately 300 miles west-northwest of Shemya: 50 knot winds, with blowing spray (which is plotted with the symbol normally used to indicate blowing sand).

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

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

Model fields indicated that the height of the Dynamic Tropopause — taken to be the pressure of the PV1.5 surface — descended to the 600 hPa pressure level as the storm moved across the Shemya area (below).

GOES-17 Mid-level Water Vapor (6.9 µm) images, with contours of PV1.5 pressure [click to play animation | MP4]

GOES-17 Mid-level Water Vapor (6.9 µm) images, with contours of PV1.5 pressure [click to play animation | MP4]

Of particular significance was the fact that a new low pressure record for the State of Alaska was set when Shemya dropped to 924.8 hPa at 2159 UTC (below).

Plot of surface report data from Shemya [click to enlarge]

Plot of surface report data from Shemya [click to enlarge]



Categories: GOES-17, Metop, Red-Green-Blue (RGB) images, Satellite winds, Suomi NPP, VIIRS