December 1st, 2021 | Scott Bachmeier
NOAA-20 True Color RGB and Infrared Window (11.45 µm) images viewed using RealEarth (above) showed a large convective burst south of the center of Tropical Storm Nahtoh — located in the Philippine Sea — at 0356 UTC on 01 December 2021. A robust overshooting top near the center of the convective burst exhibited a cluster of cloud-top infrared brightness temperatures of -100ºC and colder (red pixels embedded within purple-to-yellow-to-black enhancement).
2.5-minute rapid scan JMA Himawari-8 Infrared Window (10.4 µm) images (below) displayed the evolution of Nyatoh as it transitioned from a Tropical Storm to a Category 1 Typhoon at 1200 UTC. The coldest cloud-top infrared brightness temperatures of convective overshooting tops were in the -90 to -98ºC range, but did not quite reach the -100ºC threshold that was seen in the VIIRS imagery.