Pyrocumulonimbus clouds produced by the Mullen Fire in Wyoming

September 19th, 2020 |

GOES-16 “Red” Visible (0.64 µm, top), Shortwave Infrared (3.9 µm, center) and “Clean” Infrared Window (10.35 µm, bottom) images, with hourly plots of surface reports [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm, top), Shortwave Infrared (3.9 µm, center) and “Clean” Infrared Window (10.35 µm, bottom) images, with hourly plots of surface reports [click to play animation | MP4]

GOES-16 (GOES-East) “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm) and “Clean” Infrared Window (10.35 µm) images (above) showed a series of pyrocumulonimbus (pyroCb) pulses emanating from the Mullen Fire in southeastern Wyoming on 19 September 2020. Each of the  pulses exhibited 10.35 µm brightness temperatures of -40ºC and colder  (shades of blue) — assuring the heterogeneous nucleation of all supercooled water droplets to form ice crystals, thereby meeting the criteria of a pyroCb.

The coldest cloud-top infrared brightness temperatures were around -47ºC, which corresponded to altitudes near 11 km according to rawinsonde data from Riverton, Wyoming (below).

Plot of 00 UTC rawinsonde data from Riverton, Wyoming [click to enlarge]

Plot of 00 UTC rawinsonde data from Riverton, Wyoming [click to enlarge]

Northern California’s Bear Fire produces a pyrocumulonimbus cloud

September 9th, 2020 |

GOES-17 “Red” Visible (0.64 µm, top left), Shortwave Infrared (3.9 µm, top right), Fire Temperature RGB + GLM Flash Extent Density (bottom left) and “Clean” Infrared Window (10.35 µm, bottom right) [click to play animation | MP4]

GOES-17 “Red” Visible (0.64 µm, top left), Shortwave Infrared (3.9 µm, top right), Fire Temperature RGB + GLM Flash Extent Density (bottom left) and “Clean” Infrared Window (10.35 µm, bottom right) [click to play animation | MP4]

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.

Suomi NPP VIIRS Day/Night Band (0.7 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images [click to enlarge]

Suomi NPP VIIRS Day/Night Band (0.7 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images [click to enlarge]

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).

Infrared Window images from Suomi NPP (11.45 µm) and GOES-17 (11.45 µm) [click to enlarge]

Infrared Window images from Suomi NPP (11.45 µm) and GOES-17 (10.35 µm) [click to enlarge]

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.

GOES-17 True Color RGB images [click to pay animation | MP4]

GOES-17 True Color RGB images [click to pay animation | MP4]

2 pyrocumulonimbus events in Northern California

September 8th, 2020 |

GOES-17 “Red” Visible (0.64 µm, top left), Shortwave Infrared (3.9 µm, top right), Fire Temperature RGB + GLM Flash Extent Density (bottom left) and “Clean” Infrared Window (10.35 µm, bottom right) [click to play animation | MP4]

GOES-17 “Red” Visible (0.64 µm, top left), Shortwave Infrared (3.9 µm, top right), Fire Temperature RGB + GLM Flash Extent Density (bottom left) and “Clean” Infrared Window (10.35 µm, bottom right) [click to play animation | MP4]

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.

GOES-16 “Red” Visible (0.64 µm, top left), Shortwave Infrared (3.9 µm, top right), Fire Temperature RGB + GLM Flash Extent Density (bottom left) and “Clean” Infrared Window (10.35 µm, bottom right) [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm, top left), Shortwave Infrared (3.9 µm, top right), Fire Temperature RGB + GLM Flash Extent Density (bottom left) and “Clean” Infrared Window (10.35 µm, bottom right) [click to play animation | MP4]

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.

GOES-17 “Red” Visible (0.64 µm, top left), Shortwave Infrared (3.9 µm, top right), Fire Temperature RGB + GLM Flash Extent Density (bottom left) and “Clean” Infrared Window (10.35 µm, bottom right) [click to play animation | MP4]

GOES-17 “Red” Visible (0.64 µm, top left), Shortwave Infrared (3.9 µm, top right), Fire Temperature RGB + GLM Flash Extent Density (bottom left) and “Clean” Infrared Window (10.35 µm, bottom right) [click to play animation | MP4]

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).

GOES-16 “Red” Visible (0.64 µm, top left), Shortwave Infrared (3.9 µm, top right), Fire Temperature RGB + GLM Flash Extent Density (bottom left) and “Clean” Infrared Window (10.35 µm, bottom right) [click to play animation | MP4]

GOES-16 “Red” Visible (0.64 µm, top left), Shortwave Infrared (3.9 µm, top right), Fire Temperature RGB + GLM Flash Extent Density (bottom left) and “Clean” Infrared Window (10.35 µm, bottom right) [click to play animation | MP4]

Fast-moving wildfires in Washington State

September 7th, 2020 |

GOES-17 “Red” Visible (0.64 µm, top left), Shortwave Infrared (3.9 µm, top right), Fire Temperature RGB + GLM Flash Extent Density (bottom left) and “Clean” Infrared Window (10.35 µm, bottom right) [click to play animation | MP4]

GOES-17 “Red” Visible (0.64 µm, top left), Shortwave Infrared (3.9 µm, top right), Fire Temperature RGB + GLM Flash Extent Density (bottom left) and “Clean” Infrared Window (10.35 µm, bottom right) [click to play animation | MP4]

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.