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Elsa briefly regains hurricane intensity before making landfall along the Florida coast

By Scott Bachmeier •

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

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

Late in the day on 06 July 2021, Tropical Storm Elsa regained hurricane intensity as of 0000 UTC, just off the west coast of Florida. 1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm) and “Clean” Infrared Window (10.35 µm) images (above) showed the tropical cyclone during the 1500 UTC to 0000 UTC time period. In the morning, cloud-top infrared brightness temperatures of -80ºC or colder were seen (violet pixels), but during most of the day they were in the -70 to -79ºC range. While Elsa had been moving over water with Sea Surface Temperature values around 28ºC, the Ocean Heat Content of those waters was relatively low.

For a few hours the low-level circulation of Elsa remained exposed from its deep convection to the northeast — and GOES-16 Visible images with an overlay of deep-layer shear at 1800 UTC, from the CIMSS Tropical Cyclones site (below), showed that this was due to westerly shear values around 25-30 knots over the area.

GOES-16 “Red” Visible (0.64 µm) images, with an overlay of deep-layer wind shear at 1800 UTC [click to enlarge]

GOES-16 “Red” Visible (0.64 µm) images, with an overlay of deep-layer wind shear at 1800 UTC [click to enlarge]

The center of Elsa moved just to the east of Buoy 42023 — a plot of wind speed/gust and pressure is shown below.

Plot of wind speed/gusts and pressure at Buoy 42023

Plot of wind speed/gusts and pressure at Buoy 42023

A DMSP-15 Microwave (85 GHz) Microwave image at 2155 UTC (below) indicated that Elsa had nearly completed the formation  of a closed eyewall at that time.

DMSP-15 Microwave (85 GHz) Microwave image at 2155 UTC [click to enlarge]

DMSP-15 Microwave (85 GHz) Microwave image at 2155 UTC [click to enlarge]

GOES-16 Infrared  / Water Vapor Difference images (below) revealed pockets of stronger overshooting tops near the center of deep convection during the hours leading up to Elsa reaching hurricane intensity.

GOES-16 Infrared / Water Vapor Difference images [click to enlarge]

GOES-16 Infrared  / Water Vapor Difference images [click to enlarge]

===== 07 July Update =====

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

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

After once again weakening to Tropical Storm intensity at 0600 UTC, Elsa eventually made landfall along the coast of Florida around 1500 UTC on 07 July, as seen in 1-minute GOES-16 Visible and Infrared images (above) — inland impacts included an EF0 tornado, wind gusts to 71 mph and rainfall exceeding 11 inches (NWS Public Information Statements).

At 1223 UTC, a DMSP-17 SSMIS Microwave image (below) indicated that a closed eyewall was not present with Elsa at that time.

DMSP-17 SSMIS Microwave (85 GHz) image [click to enlarge]

DMSP-17 SSMIS Microwave (85 GHz) image [click to enlarge]

Categories: DMSP, GOES-16, Microwave, Satellite winds, Tropical cyclones