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Pyrocumulonimbus clouds spawned by a wildfire in British Columbia

By Scott Bachmeier •

10-minute GOES-18 Clean Infrared Window (10.3 µm, left) images and Red Visible (0.64 µm) images + Fire Mask derived product (right), from 2000 UTC on 28 May to 0500 UTC on 29 May [click to play MP4 animation]

10-minute Full Disk scan GOES-18 (GOES-West) “Clean” Infrared Window (10.3 µm) images and “Red” Visible (0.64 µm) images with an overlay of the FDCA Fire Mask derived product (above) showed that a large wildfire north of Fort Nelson (CYYE) in far northeastern British Columbia produced a series of ~3 pyrocumulonimbus (pyroCb) clouds on 28 May 2025. The pyroCb clouds exhibited cloud-top 10.3 µm infrared brightness temperatures (IRBTs) in the -40s C (denoted by shades of blue to cyan) — a necessary condition to be classified as a pyroCb — beginning at 0010 UTC on 29 May. The coldest pyroCb cloud-top IRBT was -52.57ºC at 0320 UTC on 29 May (below).

GOES-18 Clean Infrared Window (10.3 µm, left) image and Red Visible (0.64 µm) image + Fire Mask derived product (right), with a cursor sample of the coldest cloud-top infrared brightness temperature at 0320 UTC on 29 May [click to enlarge]

According to rawinsonde data from Fort Nelson, British Columbia at 0000 UTC on 29 May (below), the coldest pyroCb IRBT corresponded to an altitude around 11.1 km.

Plot of rawinsonde data from Fort Nelson, British Columbia at 0000 UTC on 29 May [click to enlarge]

This large wildfire burned very hot, exhibiting Shortwave Infrared 3.9 µm brightness temperature values of 137.88ºC — the saturation temperature of GOES-18 ABI Band 7 detectors — for 2.5 hours, from 2210 UTC on 28 May (2 hours prior to the formation of the first pyroCb) until 0040 UTC on 29 May (below).

Cursor sample of GOES-18 Shortwave Infrared (3.9 µm) brightness temperature (left panel) at 2210 UTC on 28 May [click to enlarge]

Cursor sample of GOES-18 Shortwave Infrared (3.9 µm) brightness temperature (left panel) at 0040 UTC on 29 May [click to enlarge]

This wildfire also made a significant run to the NNW in ~13 hours, as seen in a comparison of VIIRS Fire Radiative Power displayed using RealEarth (below).

VIIRS Fire Radiative Power at 2138 UTC on 28 May and 1039 UTC on 29 May [click to enlarge]

The NNW run of the wildfire was also apparent in a 14-hour animation of Next Generation Fire System (NGFS) fire detection polygons (below).

10-minute GOES-18 Infrared Window images with an overlay of NGFS Fire Detection polygons, from 1900 UTC on 28 May to 0900 UTC on 29 May [click to play MP4 animation]

===== 29 May Update =====

10-minute GOES-19 True Color RGB images, from 1100 UTC on 29 May to 0050 UTC on 30 May [click to play MP4 animation]

During the following daytime hours, GOES-19 (GOES-East) True Color RGB images (above) revealed a long ribbon of brownish-gray smoke-laden pyroCb ice cloud that was arcing eastward across the Northwest Territories then curving southward over Nunavut, Manitoba and Saskatchewan as the leading edge approached the Canada/US border.

Categories: Fire detection, GOES-18, GOES-19, NGFS, RealEarth, Red-Green-Blue (RGB) images, VIIRS