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. 

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

     

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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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The Dixie Fire (which had grown to become the largest on record for the state of California) began burning on 13 July 2021 — and on 13 August 2021, 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) showed the thermal signature (darker red to black pixels) during the 1200 UTC – 1801 UTC period. The images were displayed in the native projection of each satellite.

Although there was smoke and some clouds across the area at the time of the Suomi NPP overpass, the VIIRS False Color RGB image provided a good view of most of the fire’s large burn scar (shades of red to brown). On this day, the fire had burned nearly 518,000 acres, and was 31% contained.

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An EF-3 tornado moved through the southwest Wisconsin town of Boscobel, in Grant County, late in the afternoon of 7 August 2021 (Preliminary Storm Summary from WFO ARX). The tornado was on the ground from 4:29 to 4:56 PM CDT, or 2129 – 2156 UTC. How did the ABI imagery and GLM data change over this time? The Satellite Information Familiarization Tool (SIFT) can be used to investigate this. Gridded GLM data that can be imported into SIFT (a two-week rolling archive is available) is available at this website. ABI Radiance data can be acquired from NOAA CLASS or from the Amazon Cloud.

The GOES-16 ABI Clean Window animation from 2100 to 2159 UTC, bracketing the times that the tornado, linked to the image above, shows very strong upper-level difluence (consider how the cirrus shield spreads south in the hour of the animation!); one might infer cyclonic motion in the fields as well.

SIFT allows for the identification of regions that can then be investigated. The toggle below shows a polygon that has been defined. Subsequent plots will focus on this region surrounding the storm tops associated with the tornadic storm.

How do the cloud-top brightness temperatures evolve in that region? One way to describe that is a simple bar-graph showing the distribution of temperatures, shown below. There are three distinct cold temperature events: around 2130 UTC, around 2138 UTC, around 2148 UTC. (Recall the tornado is on the ground fron 2129-2156) The time-scale of the changes is such that only 1-minute imagery will be able to capture it accurately.

How do the lightning observations evolve in the storm? SIFT will display many different GLM parameters: Average and Minimum Flash Areas, Total Energy, Group (and Flash) Extent and Centroid Densities, Group and Flash Areas. Some are displayed below, again within the confines of the polygon defined above. The first plot compares Average Flash Area (along a constant x axis) and Total Optical Energy (along a varying y axis). The distribution in the plot seems to change during the time when the tornado is on the ground.

SIFT also allows direct comparisons between ABI and GLM data, as shown below: Flash Extent Density is compared to Band 13 (10.3 µm) brightness temperatures at discrete times within the tornado’s lifecycle.

For more information on SIFT, including download instructions for linux, MacOS and Windows, refer to the SIFT website.

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