GOES-16 sea-surface temperatures on 1 April 2021 show a region of much cooler temperatures — values around 74ºF , green in the color enhancement used) — surrounded by warmer sea-surface temperatures (values in the mid-80sºF, yellows and oranges in the color enhancement) to the southwest of Nicaragua. Why does this cool region exist? Typically, cool ocean surface temperatures can originate via upwelling (Note in the image above cool temperatures along the Equator where persistent upwelling exists). Is the part of the ocean that is cool above affected by upwelling? Cool temperatures are apparent to the northwest as a result of oceanic upwelling from a Tehuano wind through the Chivela mountain pass (similar to this event from 2018). There is a similar gap in the mountains between Costa Rica and Nicaragua (link).  Perhaps a persistent wind through that gap during the past months initiated this cool patch.  As shown below, the cool patch has been quite persistent — it was apparent in mid-January.

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The animation above cycles through GOES-16 Visible Imagery (0.64 µm) at 1901 UTC as well as simultaneous observations (from NUCAPS) of Lapse Rates (925-700 mb and 700-300 mb) and Mixing Ratio (925-700 mb and 700-300 mb). Thermodynamic information from NUCAPS complements information about the atmosphere that can be inferred by the GOES-16 imagery.

There are very strong low-level (925-700) lapse rates around Missouri behind the cold front that stretches over the south.   The atmosphere there is also very dry.  The smaller lapse rates at higher altitudes (700-300) also are in a region of very dry air.   NUCAPS Soundings from Des Moines, Kansas City and St Louis show the inversion that exists between the steep low-level lapse rates and smaller upper-level lapse rates. There is a much smaller change in lapse rates over the southeastern United States, with small stability all through the troposphere.

NUCAPS thermodynamic fields also capture the relatively moist air within the cloud features in northeastern Iowa, with strong low-level lapse rates on either side of the cloud field there.

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1-minute Mesoscale Domain Sector GOES-16 (GOES-East) Shortwave Infrared (3.9 µm) images (above) displayed the thermal anomalies (clusters of hot pixels) associated with 2 wildfires burning in western South Dakota on 29 March 2021. One fire began just west of Rapid City around 1530 UTC — which forced some evacuations. A second fire began just north of Interstate 90 around 1730 UTC — which forced the closure of Interstate 90 between Kadoka and Murdo as strong northwesterly winds in the wake of a cold frontal passage (surface analyses) caused a rapid fire run to the southeast. The southern surge of cold air (lighter shades of gray) behind the cold front could also be seen in the Shortwave Infrared images; both fires began shortly before the arrival of the cold front.

Taking a closer look at the fire just west of Rapid City, a 4-panel comparison of GOES-16 Fire Temperature RGB, Shortwave Infrared, Fire Power and Fire Temperature Characterization products (below) showed that this was not a particularly large or hot fire, whose signature was sometimes obscured by clouds moving overhead.

===== 30 March Update =====

On the following day, GOES-16 “Red” Visible (0.64 µm), Near-Infrared “Vegetation” (0.86 µm) and Day Land Cloud Fire RGB images (above) revealed the northwest-to-southeast oriented burn scar (darker gray pixels).

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NOAA’s GOES-5 VISSR view of a historical outbreak in the Carolina’s in 1984. March 28th and 29th, 1984 saw one of the most destructive tornado events in the history of North and South Carolina.

Infrared Loop:

The coldest clouds appear as darker shades of red. A regional scale IR loop.

Visible Loop:

A more zoomed-in visible loop over the same time range.

H/T Melissa Griffin for reminding us of this case:

#OTD in 1984, one of the most destructive tornado outbreaks in history, swept through the Carolinas. In all, 11 tornadoes raced across SC, including five F4 (wind estimated 207-260 mph). These tornadoes caused 15 deaths, 448 injuries, and damage of over $100 million. #scwx pic.twitter.com/fzI8wLUiAm

— Melissa Griffin (@mlgriffinWX1) March 28, 2021

More background on this case in 1984 was posted by the NWS Willmington office: https://www.weather.gov/ilm/CarolinasOutbreak.

A larger Full Disk “sandwich” image.

NOAA GOES-5 data are via the University of Wisconsin-Madison SSEC Satellite Data Services.

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