Hurricane-Force low over the Aleutian Islands

December 29th, 2018 |
Water Vapor images from GOES-17 (6.9 µm, left) and GOES-15 (6.5 µm, right) [click to play animation | MP4]

Water Vapor images from GOES-17 (6.9 µm, left) and GOES-15 (6.5 µm, right) [click to play animation | MP4]

* GOES-17 images shown here are preliminary and non-operational *

A mid-latitude cyclone moved northward over the far western Aleutian Islands late in the day on 28 December 2018, intensifying to a Hurricane Force low pressure system by 06 UTC on 29 December (surface analyses). A comparison of GOES-17 and GOES-15 (GOES-West) Water Vapor images (above) highlighted the improved spatial resolution of the GOES-17 data (2 km at satellite sub-point, vs 4 km for GOES-15). The view from GOES-15 was more oblique, since it was positioned at 128º W longitude (compared to 137.2º W longitude for GOES-17). GOES-17 is scheduled to become the operational GOES-West satellite in January 2019.

A toggle between GOES-17 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images at 1100 UTC is shown below. Although the satellite viewing angle was large, good detail could still be seen.

GOES-17 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images at 1100 UTC [click to enlarge]

GOES-17 Low-level (7.3 µm), Mid-level (6.9 µm) and Upper-level (6.2 µm) Water Vapor images at 1100 UTC [click to enlarge]

A sequence of Suomi NPP VIIRS Visible (0.64 µm), Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images (below) showed the storm as it was intensifying — the peak surface wind gust at Shemya Eareckson Air Station (PASY) was 66 knots at 1024 UTC. Since the Moon was in the Waning Gibbous phase (at 60% of Full), there was ample illumination to provide a useful “visible image at night” with the VIIRS Day/Night Band at 1403 UTC (4:03 AM local time).

Suomi NPP VIIRS Visible (0.64 µm), Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS Visible (0.64 µm), Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images [click to enlarge]

A time series plot of hourly surface weather data from Shemya during the time period of the GOES-17/15 Water Vapor image comparison is shown below, along with a more detailed time series that included Special Reports in addition to the standard Hourly Reports..

Time series plot of surface weather data from Shemya Eareckson Air Station [click to enlarge]

Time series plot of Hourly surface weather data from Shemya Eareckson Air Station [click to enlarge]

Time series plot of Hourly and Special surface weather data from Shemya Eareckson Air Station [click to enlarge]

Time series plot of Hourly and Special surface weather data from Shemya Eareckson Air Station [click to enlarge]

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