1-minute Mesoscale Domain Sector GOES-17 (GOES-West) “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm), Fire Temperature Red-Green-Blue (RGB) + GLM Flash Extent Density (FED) and “Clean” Infrared Window (10.35 µm) images (above) showed the formation of a pyrocumulonimbus (pyroCb) cloud over the Bear Fire (part of the North Complex) in Northern California on 09 September 2020. The coldest cloud-top infrared brightness temperatures were -61.4ºC; no GLM-detected lightning activity was seen with this pyroCb. 

A comparison of Suomi NPP VIIRS Day/Night Band (0.7 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images (below) displayed the initial 2 pyroCb cloud pulses shortly after their formation. Side-illumination from the Moon (which was in the Waning Gibbous phase, at 59% of Full) allowed for a distinct shadow to be cast northwest of the colder/taller pyroCb pulse — and the pyroCb clouds exhibited a darker appearance than the layer of low-altitude smoke to the west, likely due to very high amounts of fresh smoke contained within the rapidly-rising cloud turrets.

A toggle between time-matched Infrared Window images of the Bear Fire pyrocumulonimbus cloud from Suomi NPP (SNPP) and GOES-17 (below) highlighted the differences in spatial resolution — 375-m with SNPP VIIRS, vs 2-km (at satellite sub-point) with GOES-17 ABI — and the parallax displacement inherent with GOES-17 imagery at that location (17 km for a 15.2-km tall cloud top). The coldest cloud-top infrared brightness temperature was -76.2ºC with SNPP, vs -59.9ºC with GOES-17 (identical color enhancements were applied to both images).

GOES-17 True Color Red-Green-Blue (RGB) images created using Geo2Grid (below) showed the southward drift of the high-altitude pyroCb cloud material during the day, along with widespread dense smoke that covered much of California at lower altitudes.

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1-minute Mesoscale Domain Sector GOES-17 (GOES-West) “Red” Visible (0.64 µm), GOES-17 Shortwave Infrared (3.9 µm), Fire Temperature Red-Green-Blue (RGB) + GLM Flash Extent Density (FED) and “Clean” Infrared Window (10.35 µm) images (above) showed the formation of a pyrocumulonimbus (pyroCb) cloud over the Hopkins Fire in Northern California on 08 September 2020.

The vertical extent of the pyroCb cloud tower was even more apparent when viewed in Visible imagery from GOES-16 (GOES-East), displayed in the top left panel of the animation below.

Later in the day and farther to the east, 1-minute GOES-17 imagery (below) showed the development of another pyroCb cloud over the North  Complex. Unfortunately, there was a ~1-hour gap in images (from 2034 to 2130 UTC) when a yaw flip maneuver was performed on the satellite.

However, during this yaw flip maneuver the pyroCb formation and propagation could be followed using 5-minute imagery from GOES-16 (below). As the lower-latitude portion of the smoke plume associated with this fire flare-up drifted south-southwestward, it restricted the surface visibility to 2.5 miles at Beale Air Force Base (KBAB).

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1-minute Mesoscale Domain Sector GOES-17 (GOES-West) “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm), Fire Temperature Red-Green-Blue (RGB) + GLM Flash Extent Density (FED) and “Clean” Infrared Window (10.35 µm) images (above) showed the smoke plume and thermal signature of the Pearl Hill Fire — which made a rapid ~50-mile run south-southwestward across northern Washington State on 07 September 2020. During this time, northwesterly winds gusted to 40 knots (46 mph) at Omak (KOMK) near the source of the fire. Downwind of the fire, smoke reduced the visibility to 1.5 miles at times in Wenatchee (KEAT).

Later in the day, smaller fires which started burning farther to the east exhibited similar (albeit much shorter-distance) southwestward runs.

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GOES-16 Visible imagery, above, during the late afternoon on 6 September, shows an invigoration of the Cameron Peak fire in Larimer County, Colorado, with visible evidence of a pyrocumulus development.  Are there tools a forecaster can use to anticipate such extraordinary afternoon fire growth?

NOAA-20 overflew Colorado shortly after (NOAA-20 orbits can be viewed at this website) 2000 UTC on 6 September (see NUCAPS Sounding availability points below;  note that the date of these plots — 1951 UTC — corresponds to the time of  the first NUCAPS swath is available in AWIPS from this NOAA-20 pass;  for this ascending pass, that swath is near 40 S latitude!)

What do the NUCAPS Sounding surrounding Larimer County Colorado look like?  The animation below steps through the profiles surrounding the fire.  Consider using the LCL and EL information (and other information) in these profiles when diagnosing the likelihood of convection developing in response to an intense fire.  On this day, NUCAPS showed steep mid-tropospheric lapse rates that help support pyrocumulonimbus.

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