On 03 September 2017 two pyroCbs formed in the Montana. GOES-15 detected the smoke plume and pyroCb cloud, as well as the fires hot spots. The first pyroCb cloud (~45.3º N, 115.1ºW) formed around 23:00 UTC on 03 September . The second formed shortly after around 45.8º N 114.9ºE at 23:30 UTC on 03 September. Starting at 22:00 UTC on 03 September, the animation below shows GOES-15 0.63 µm visible (left) and 3.9 µm shortwave IR (right) . In the shortwave IR images, the red pixels indicate very hot IR brightness temperatures exhibited by the fire source regions.
Usually GOES-15 10.7 μm IR channel is used to find the cloud-top IR brightness temperature. However, the resolution of this satellite did not provide a brightness temperature lower than -40ºC.
A 1-km resolution NOAA-19 AVHRR 10.8 µm Infrared Window image (below;courtesy ofRené Servranckx) revealed a minimum cloud-top IR brightness temperature of -45.3º C (green color enhancement) for the first pyroCb and -45.7º C for the second (green color enhancement) at 0:43 UTC on 04 September.