Shortwave Infrared (3.9 µm) images from GOES-17, GOES-15, GOES-14 and GOES-16 [click to play animation | MP4]

The Caldor Fire (east of Sacramento, California) exhibited unprecedented growth on 17 August 2021 — increasing from 3600 acres burned in the morning to 30,000 acres that evening, with 0% containment — and Shortwave Infrared (3.9 µm) images from 1-minute GOES-17, 15 to 30-minute GOES-15, 15 to 30-minute GOES-14 and 5-minute GOES-16 (above) displayed a rapid expansion of the fire’s thermal anomaly (large cluster of hot pixels, darker black enhancement; the white pixels seen in GOES-15 images were due to a “wrap-around” effect with that satellite’s saturated 3.9 µm detectors). Each of the 4 image panels are displayed in the native projection of that particular satellite.

GOES-17 True Color RGB images created using Geo2Grid  (below) showed the large amounts of smoke (and frequent pyrocumulus clouds) produced by the Caldor Fire.  

GOES-17 True Color RGB images [click to play animation | MP4]

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GOES-16 “Cirrus” channel (1.38 µm) imagery, above, and visible (0.64 µm ), below, shows Tropical Storm Henri to the southeast of the island of Bermuda (at 32.3º N, 64.7º W) shortly after sunrise on 17 August 2021. The cirrus channel shows a compact region of convection and an expanding cirrus shield. Visible imagery, below (click here for the animation in CSPP Geosphere), at a higher resolution (and zoomed in) also shows persistent convection near the center of the storm (according to NHC at 1500 UTC: 30.4º N, 64.3º W). The curvature of the low-level clouds in the visible imagery, below, give some hint to where the surface center is, near the western edge of the convection. (Those low-level clouds are not visible in the ‘Cirrus’ channel animation above because water vapor is absorbing reflected solar radiation at 1.38 µm and the signal from the low clouds is lost).

An analysis of shear at 1500 UTC on 17 August (here, from the CIMSS Tropical site) shows modest northerly shear over the storm.

For more information on Henri, refer to the National Hurricane Center. Current forecasts keep the storm offshore, although swells from the storm could affect beaches along the eastern seaboard of the USA.

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GOES-16 “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images [click to play animation | MP4]

1–minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (above) showed Tropical Storm Fred during the 8-hour period leading up to it making landfall along the panhandle of Florida around 1915 UTC on 16 August 2021. Multiple convective bursts developed near the storm center, with some exhibiting cloud-top infrared brightness temperatures of -80ºC or colder (violet pixels). As Fred moved inland, it produced heavy rainfall and strong winds.

A time-matched comparison of Infrared images from GOES-16 and Suomi NPP at 1831 UTC is shown below. The coldest cloud-top infrared brightness temperatures were -74.1ºC with GOES-16 and -79.5ºC with Suomi NPP. The spatial offset is due to parallax that is inherent with GOES imagery. 

1831 UTC Infrared Window images from GOES-16 (10.35 µm) and Suomi NPP (11.45 µm) [click to enlarge]

Views of Fred from 4 GOES (GOES-17, GOES-15, GOES-14 and GOES-16) around 1800 UTC are shown below. 

Infrared Window images of Tropical Storm Fred from GOES-17, GOES-15, GOES-14 and GOES-16 around 1800 UTC (credit: Tim Schmit, NOAA/NESDIS/ASPB) [click top enlarge]

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VIIRS Imagery from Suomi-NPP (the Day Night Band, at 0.7 µm and I05, at 11.5 µm, above, at 0704 UTC) and from NOAA-20 (the Day Night Band, at 0.7 µm and I05, at 11.5 µm, below, at 0754 UTC), show polar orbiting perspectives of Tropical Storm Fred. The Day Night Band shows little detail in the cloud-tops, given the lack of lunar illumination (the moon — about half-illuminated — was below the horizon during these overpasses). The region of coldest cloud tops seems to have decreased from the NPP to the NOAA-20 overpass. The NHC discussion at 0300 UTC suggested that the low-level circulation had emerged from underneath the cirrus canopy, and perhaps that’s detectable in the toggles above and below. The storm does exist under southwesterly shear (morning analysis from the CIMSS Tropical Website).

Microwave data from the Advanced Technology Microwave Sounder (ATMS) on board both Suomi-NPP and NOAA-20 can be used to compute a rain rate, as shown below. The Rain Rate snapshots show a decrease in intensity between 0704 (a maximum of about 0.9″/hour) and 0754 UTC (a maximum of 0.5″/hour). That information, combined with the lack of observed lightning in the Day Night Band, might help guide an analyst in their description of the storm strength. Consider, however, that NPP had a near-nadir view whereas NOAA-20 was an edge view.

VIIRS imagery and the ATMS Rain Rate is available in AWIPS-ready tiles via the CIMSS ldm feed. Imagery from Polar Orbiters over Fred (and Grace, and TD #8 (now Henri) in the Atlantic) is also available from the AOML Direct Broadcast link here.

For more information on Tropical Storm Fred, refer to the National Hurricane Center. Fred is forecast to make landfall on the Florida panhandle on 16 August.

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