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Idalia becomes a Hurricane

By Scott Bachmeier •

NOAA-20 VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images valid at 0735 UTC [click to enlarge]

A toggle between NOAA-20 (mislabeled as NPP) VIIRS Day/Night Band (0.7 µm) and Infrared Window (11.45 µm) images valid at 0735 UTC on 29 August 2023 (above) showed Tropical Storm Idalia about 1.5 hours before it reached Category 1 hurricane intensity at 0900 UTC. A large convective burst was evident just northeast of the storm center.

Overlapping 1-minute Mesoscale Domain Sectors provided 30-second GOES-16 “Clean” Infrared Window (10.3 µm) images (with/without an overlay of GLM Flash Extent Density) and “Red” Visible (0.64 µm) images during the 10-hour period from 1000-2000 UTC (below). Cloud-top infrared brightness temperatures were as cold as -90C (yellow pixels embedded within darker purple areas) — and occasional bursts of lightning activity were seen.

30-second GOES-16 “Clean” Infrared Window (10.3 µm) images (with/without an overlay of GLM Flash Extent Density) and “Red” Visible (0.64 µm) images, 1000-2000 UTC [click to play MP4 animation]

Odalia had been moving northward across warm Sea Suface Temperatures, and intensified to a hurricane as it traversed a ribbon of high Ocean Heat Content. According to deep-layer wind shear analyses from the CIMSS Tropical Cyclones site (below), Odalia was also moving through an environment of low shear (another factor favorable for intensification).

GOES-16 Water Vapor images, with analyses of deep-layer wind shear [click to enlarge]

Categories: GLM, GOES-16, Lightning, NOAA-20, Satellite winds, Tropical cyclones, VIIRS