Pyrocumulonimbus clouds in AlaskaA sequence of Suomi-NPP VIIRS Visible (0.64 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images at 2149 UTC and 2332 UTC (above) showed “before” and “after” views of a pyrocumulonimbus (pyroCb) cloud that developed south of McGrath, Alaska late in the day on 11 June 2022. The coldest cloud-top infrared brightness temperature of the pyroCb cloud on the 2332 image was -48C.
A couple of hours later, preliminary / non-operational GOES-18 “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm) and “Clean” Infrared Window (10.35 µm) images (below) showed that the Little Hog Butte Fire — located southwest of Lake Minchumina (PAMH) — produced a larger and more long-lived pyroCb cloud, which then drifted east-northeastward from the fire source region. The coldest cloud-top infrared brightness temperature of that pyroCb cloud was around -48C. Smoke from this fire was reducing the surface visibility to 2 miles at times at Lake Minchumina. Particularly noteworthy was the fact that this was the first documented pyroCb over Alaska in 2 years.