Very dry and breezy conditions developed across southeast Colorado during the afternoon of 20 May 2020 ahead of a broad western US upper trough and behind a surface dryline. With deep vertical mixing occurring behind the dryline, RH values fell to around 10 %, and winds gusted 30-40 knots. A wildland grass fire initiated north of Kim, CO during the early afternoon.
A GOES-East 1-min meso sector was available over a region including the wildfire during the day in support of convective warning operations (Fig 1). A watchful eye would notice the flickering of a faint hot spot below thin cirrus clouds by around 1945 UTC. With 5x more images , a forecaster can be more confident in wildfire detection earlier when using 1-min imagery over 5-min imagery. A simple gray-scale color table applied to ABI single-band 3.9 um imagery has proven to be a very reliable method for detecting wildfire starts, especially when 1-min imagery is available.
Later, as the fire continued to grow, an impressive smoke plume developed. The 1-min visible imagery shows the rapid growth of the plume, and even development of pyrocumulus adjacent to a colder cloud shield. IRW brightness temperatures associated with the pyrocu reached -20C shortly after 0100 UTC.
A long animation of the wildfire combines visible, SWIR and IRW imagery along with RAP surface analysis RH and wind gust fields for the duration of the event. The animation shows the fire initiating as wind gust speeds increase over 30 knots and RH values drop below 15%. The fire continues to burn hot well after sunset, before decreasing in intensity as wind speeds died down and RH values rose.
A 4-panel image of the wildfire and smoke plume during the early evening provides a variety of unique RGB displays for tracking the hot spot and associated smoke plume in unison. At this time, the hot spot was quite expansive, and pyrocumulus developing within the smoke plume.
S-NPP and NOAA-20 VIIRS imagery also captured the wildfire during it’s early stages, and during the evening. The same gray scale color table is used for each VIIRS/ABI image pair.
The 375 m I-4 band (3.74 um) imagery captured the wildfire earlier than was possible in the 2-km ABI imagery, and pinpointed it to a smaller region (a single dark pixel at 1915 UTC; Fig 5). At 2000 UTC, the fire had spread to a few pixels, but was still quite faint in the ABI imagery. However, as was shown, the animations of 1-min ABI imagery (not possible with VIIRS) allowed for confident detection of a hot spot by this point. By 2051 UTC, the wildfire hot spot was obvious in both VIIRS and ABI, but with VIIRS narrowing down the location to a much smaller area.
During the evening, both instruments continue to detect heat associated with the wildfire/burned area, with VIIRS pinpointing the burn region more precisely (Fig 6).
Bill Line (NESDIS and CIRA) and Mike Umscheid (NWS DDC)
