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).

View only this post Read Less

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.

View only this post Read Less

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.

View only this post Read Less

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “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 2 distinct pulses of pyrocumulonimbus (pyroCb) cloud emanating from the Cameron Peak Fire in north-central Colorado on 06 September 2020. The coldest cloud-top infrared brightness temperatures were -52.4ºC. Smoke was occasionally restricting the surface visibility to 2 miles at Boulder (KBJC) and 2.5 miles at Fort Collins (KFNL).

This fire also produced a brief pyroCb cloud on the previous day (below), as shown by a single blue (-40ºC) pixel on the 10.35 µm image at 2301 UTC — however, since no Mesoscale Sector was positioned over the area, the fire was only sampled by 5-minute CONUS Sector images. The presence of cloud-top infrared brightness temperatures of -40ºC and colder assures heterogeneous nucleation of all supercooled water droplets to form ice crystals, thereby meeting the criteria of a pyroCb.

===== 07 September Update =====

As the fire continued burning into the nighttime hours, Suomi NPP VIIRS Shortwave Infrared (3.74 µm) and Day/Night Band (0.7 µm) images (above) displayed the fire around 0916 UTC or 2:16 am PDT on 07 September. Reflected illumination from the Moon — in the Waning Gibbous phase, at 76% of Full — allowed some of the eastward-drifting smoke to be seen.

A toggle between Shortwave Infrared images from Suomi NPP VIIRS (3.74 µm) and GOES-16 ABI (3.9 µm) is shown below — the shape of the Cameron Peak Fire thermal anomaly as well as locations of ongoing hot fires along its perimeter were more accurately seen in the 375-m resolution VIIRS image, compared to the 2-km resolution (at satellite sub-point) ABI image. The 2 images are time-matched to correspond to the 0922 UTC time of the Suomi NPP satellite’s overpass.

View only this post Read Less