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Tropical Storm Delta becomes a Hurricane over the Caribbean Sea

By Scott Bachmeier •

GOES-16 “Clean” Infrared Window (10.35 µm) images (with and without an overlay of GLM Flash Extent Density)and

GOES-16 “Clean” Infrared Window (10.35 µm) images (with and without an overlay of GLM Flash Extent Density) and “Red” Visible (0.64 µm) images [click to play animation | MP4]

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Clean” Infrared Window (10.35 µm) images — with and without an overlay of GLM Flash Extent Density — and “Red” Visible (0.64 µm) images (above) showed showed an impressive convective burst near the center of Tropical Storm Delta, which developed a couple of hours before the storm reached Category 1 Hurricane intensity at 0000 UTC on 06 October over the Caribbean Sea. There was no GLM-detected lightning activity near the center of Delta during this 2100-0100 UTC time period.

A toggle between GOES-16 Infrared and Visible images at 2156 UTC (below) revealed a small tropical overshooting top near the center of the developing convective burst — which exhibited a cloud-top infrared brightness temperature as cold as -93.2ºC (yellow pixels embedded within the darker shades of purple).

GOES-16 “Clean” Infrared Window (10.35 µm) images (with an overlay of GLM Flash Extent Density) and "Red" Visible (0.64 µm) images at 2156 UTC [click to enlarge]

GOES-16 “Clean” Infrared Window (10.35 µm) images (with an overlay of GLM Flash Extent Density) and “Red” Visible (0.64 µm) images at 2156 UTC [click to enlarge]

===== 06 October Update =====

GOES-16 “Clean” Infrared Window (10.35 µm) images (with and without an overlay of GLM Flash Extent Density) and “Red” Visible (0.64 µm) images [click to play animation | MP4]

GOES-16 “Clean” Infrared Window (10.35 µm) images (with and without an overlay of GLM Flash Extent Density) and “Red” Visible (0.64 µm) images [click to play animation | MP4]

Hurricane Delta rapidly intensified to a Category 4 storm at 1520 UTC on 06 October — with 1-minute GOES-16 Infrared and Visible images (above) showing evidence of a more organized eye and eyewall structure, including a notable amount of lightning activity near the core of the storm.

GOES-16 Infrared Window (11.2 µm) images from the CIMSS Tropical Cyclones site (below) indicated that Delta was moving through an environment of low deep-layer wind shear as the hurricane was moving over water possessing very high ocean heat content.

GOES-16 Infrared Window (11.2 µm) images, with an overlay of deep-layer wind shear [click to enlarge]

GOES-16 Infrared Window (11.2 µm) images, with an overlay of deep-layer wind shear [click to enlarge]

===== 07 October Update =====

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

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

A comparison Suomi NPP VIIRS Infrared Window (11.45 µm) and Day/Night Band (0.7 µm) images (above) revealed a small area with cloud-top infrared brightness temperatures as cold as -100.9ºC (within the small cluster of red pixels) just east of the island of Cozumel, Mexico. Even though Delta was still moving over water possessing very high ocean heat content, its intensity was reduced from Category 4 to Category 3 around this time.

A time-matched comparison of Infrared images from Suomi NPP and GOES-16 is shown below; a cloud-top infrared brightness temperature of -95.8ºC was sensed by GOES-16. There was significant parallax associated with the Suomi NPP image, since Hurricane Delta was located along the far western edge of the descending overpass swath. The same color enhancement is applied to both images.

Infrared images from Suomi NPP and GOES-16 [click to enlarge]

Infrared images from Suomi NPP and GOES-16 [click to enlarge]

Categories: GOES-16, Lightning, Suomi NPP, Tropical cyclones, VIIRS