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Pyrocumulonimbus clouds produced by wildfires in British Columbia and Alberta

By Scott Bachmeier •

GOES-18 “Red” Visible (0.64 µm) + Fire Power derived product (top left), Shortwave Infrared (3.9 µm, top right), “Clean” Infrared Window (10.3 µm, bottom left) and Day Land Cloud Fire RGB (bottom right), from 2150 UTC on 15 September to 0110 UTC on 16 September [click to play animated GIF | MP4]

10-minute GOES-18 (GOES-West) “Red” Visible (0.64 µm) + Fire Power derived product (a component of the GOES Fire Detection and Characterization Algorithm FDCA), Shortwave Infrared (3.9 µm), “Clean” Infrared Window (10.3 µm) and Day Land Cloud Fire RGB images (above) showed a wildfire east of Fort Nelson (CYYE) in far northeastern British Columbia that produced 3 consecutive pyrocumulonimbus (pyroCb) cloud pulses late in the day on 15 September 2023. This wildfire burned very hot — 3.9 µm shortwave infrared brightness temperatures reached 137.88ºC (the saturation temperature of GOES-18 ABI Band 7 detectors) at 2350 UTC, with a Fire Power value at that time of 6282.52 MW (below).

Cursor-sampled values of GOES-18 “Red” Visible (0.64 µm) + Fire Power derived product (top left), Shortwave Infrared (3.9 µm, top right), “Clean” Infrared Window (10.3 µm, bottom left) and Day Land Cloud Fire RGB (bottom right), at 2350 UTC on 15 September [click to enlarge]

A closer look at GOES-18 Shortwave Infrared images (below) showed the rapid east-southeastward run of the pyroCb-producing British Columbia wildfire. For nearly 4 hours, the peak 3.9 µm brightness temperature of that large fire remained at 137.88ºC (from 2350 UTC on 15 September to 0340 UTC on 16 September).

GOES-18 Shortwave Infrared (3.9 µm) images, from 2100 UTC on 15 September to 0700 UTC on 16 September [click to play animated GIF | MP4]

In a longer animation of GOES-18 Infrared Window images covering a larger area (below), a total of 5 distinct pyroCb clouds were produced by the British Columbia wildfire — while farther to the east, another fire in northwestern Alberta (located just south of Rainbow Lake, CWSH) later produced 2 pyroCb clouds. Strong surface winds (with gusts as high as 35 knots at Fort Nelson) associated with the approach and passage of a cold front likely played a role in intensifying wildfire behavior that led to these pyroCb formations.

GOES-18 “Clean” Infrared Window (10.3 µm) images, with 15-minute METAR surface reports plotted in yellow and 3-hour Surface Frontal Analyses plotted in blue, from 2200 UTC on 15 September to 1000 UTC on 16 September [click to play animated GIF | MP4]

The first (and largest) of the Alberta pyroCb clouds passed near/over the High Level Airport (CYOJ), where a thunderstorm was reported from 0603-0652 UTC (below). In addition, smoke from the nearby wildfire restricted surface visibility at CYOJ to 2-1/4 miles at one point.

GOES-18 “Clean” Infrared Window (10.3 µm) images from 0600-0650 UTC on 16 September, with cursor-sampled METAR reports from High Level, Alberta (CYOJ) [click to enlarge]

A toggle between VIIRS Infrared Window (11.45 µm) images from NOAA-20 at 0828 UTC and Suomi-NPP at 0919 UTC (below) showed the northward transport of the first (large, elongated) Alberta pyroCb as it crossed over the Alberta / Northwest Territories border just ahead of the approaching cold front. The second (much smaller) Alberta pyroCb was apparent in the earlier NOAA-20 image, just behind the cold front. VIIRS data used to create those 2 images were downloaded and processed by the CIMSS/SSEC Direct Broadcast ground station.

VIIRS Infrared Window (11.45 µm) images from NOAA-20 (valid at 0828 UTC) and Suomi-NPP (valid at 0919 UTC) [click to enlarge]

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GOES-18 True Color RGB images [click to play MP4 animation]

After sunrise, a cyclonic gyre of dense wildfire smoke (shades of tan to light brown) was seen moving eastward across the Northwest Territories toward Nunavut in True Color RGB images (source) from both GOES-18 (above) and GOES-16 (below). Boundary layer smoke from widespread fires on the previous day became entrained into the circulation of a low pressure system (surface analyses).

GOES-16 True Color RGB images [click to play MP4 animation]

A Suomi-NPP VIIRS True Color RGB valid at 1912 UTC — viewed using RealEarth — is shown below.

Suomi-NPP VIIRS True Color RGB image valid at 1912 UTC [click to enlarge]

Categories: Air quality, Fire detection, GOES-16, GOES-18, NOAA-20, RealEarth, Red-Green-Blue (RGB) images, Suomi NPP, VIIRS