The East Troublesome Fire, in Grand County, Colorado near Grand Lake and west of Rocky Mountain National Park, experienced substantial growth during the afternoon/evening of 21 October 2020. Dry environmental and fuel conditions, along with gusty winds, caused the fire to grow from 19,086 acres to 125,602 acres during the 1-day timeframe per Inciweb (see maps below).
GOES-East imagery captured the rapid growth of the associated hot spot signature. Throughout the event, NWS Boulder shared GOES-East imagery of the fire on social media to help inform the public of it’s evolution as it quickly spread east. A couple examples are shown below.
VIIRS imagery from the early afternoon captured the wildfire as it began it’s rapid growth (Fig 1). The Fire Radiative Power product provided a high resolution view of the heat associated the fire, highlighting a particularly active zone over the northeast portion of the fire (which would go on to continue to expand east rapidly). The underlay of VIIRS True Color imagery shows the associated smoke plume with pyrocu developing near the hot spot. This imagery is available online from the JSTAR mapper.
The daytime evolution of the wildfire is shown through the GOES-East Natural Color Fire RGB in Figure 2. The rapid growth of the wildfire hot spot is observed to begin after 2000 UTC, with the large smoke plume extending well east. Ashfall was abundant across downstream locations such as Fort Collins and Loveland. Pyrocumulus clouds were also present with the smoke plume. The large burn scar associated with the Cameron Peak Fire, north of Estes Park, is apparent, along with several other smaller burn scars throughout the scene.
A VIS-IR-SWIR combo animation extending after sunset highlights the development of the smoke plume, including eventual cooling of pyrocu to as cold as -60C after dark (Fig 3).
Long animations of GOES-East SWIR and Fire Temperature RGB show the full evolution of the wildfire hot spot growth on the 21st from Noon through around midnight (Fig 4-5). Steady growth/heating is observed through teh afternoon, before the rapid acceleration east after dark to near the Continental Divide. west of Rocky Mountain National Park.
Similar time periods but zoomed out images provide another perspective of the large growth and massive size of the fire (Fig 6-7).
The fire becomes so hot in areas that the signal in SWIR channel becomes saturated. This is a situation where the Fire Temperature RGB becomes a little more useful for those wishing to monitor fire heating trends the most active/hottest regions of the wildfire. Figure 8 from 0131 UTC compares SWIR with Fire Temperature RGB, exemplifying the power of the RGB to reveal more detailed temperature information after the SWIR channel becomes saturated. While the SWIR saturates, the Fire Temp RGB shows progressively hotter regions from red to yellow to white through it’s inclusion of the 2.2 um and 1.6 um bands, in addition to the SWIR.
GOES-West similarly displayed the evolution of the wildfire through the afternoon/evening (Fig 9).
A couple hours after midnight, SNPP and NOAA-20 VIIRS DNB NCC imagery revealed the glow of the now very large hot spot associated with the East Troublesome Fire, as well as the most active areas (Fig 10). The massive size can be compared with the City of Denver to the east.
Figure 10: 22 Oct 2020 SNPP (top) and NOAA-20 (Bottom) VIIRS DNB NCC. Higher res top, higher res bottom
The VIIRS Fire Radiative Power Product, shown earlier in this post, is also available at night, and shown in Figure 11. Again, the product provides a higher resolution view of the current location of the wildfire, along with the hottest areas.
Bill Line, NESDIS and CIRA
Satellite Liaison Blog 
