Multiple pyrocumulonimbus clouds produced by the East Troublesome Fire in Colorado

October 21st, 2020 |

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

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

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm), “Clean” Infrared Window (10.35 µm) and Fire Temperature Red-Green-Blue (RGB) images (above) showed a period of extreme behavior of the East Troublesome Fire in Colorado around and just after sunset on 21 October 2020. This rapidly-growing wildfire produced a series of pyrocumulonimbus (pyroCb) clouds — the coldest cloud-top 10.35 µm infrared brightness temperatures were -65.1ºC (darker green enhancement). The hottest Shortwave Infrared brightness temperatures within the large thermal anomaly were 138.7ºC — which is the saturation temperature of the 3.9 µm detectors on GOES-16.

=====22 October Update =====

A time-matched comparison of Shortwave Infrared images from Suomi NPP VIIRS (3.74 µm) and GOES-16 ABI (3.9 µm), valid at 0839 UTC on 22 October, is shown below. The finer spatial resolution of VIIRS (375 meters at nadir, vs 2 km for ABI) provided a more accurate depiction of the location of hottest fire pixels at that time. Note the amount of northwestward parallax shift of the cold (dark blue to violet) high clouds on the GOES-16 image.

Shortwave Infrared images from Suomi NPP VIIRS (3.74 µm) and GOES-16 ABI (3.9 µm), valid at 0839 UTC [click to enlarge]

Shortwave Infrared images from Suomi NPP VIIRS (3.74 µm) and GOES-16 ABI (3.9 µm), valid at 0839 UTC [click to enlarge]

During the subsequent daytime hours, GOES-16 Visible, Shortwave Infrared, Infrared Window and Fire Temperature RGB images (below)  showed another series of pyroCb clouds that were produced by the East Troublesome Fire — but not to the extent that was seen on 21 October. By early evening, the total burned area had increased to 170,163 acres (and was only 5% contained).

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

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

Two high-resolution views of some of the pyroCb clouds and the fire’s thermal anomaly were provided by VIIRS Visible (0.64 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images from NOAA-20 at 1904 UTC and Suomi NPP at 1956 UTC (below).

VIIRS Visible (0.64 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images from NOAA-20 and Suomi NPP [click to enlarge]

VIIRS Visible (0.64 µm), Shortwave Infrared (3.74 µm) and Infrared Window (11.45 µm) images from NOAA-20 and Suomi NPP [click to enlarge]

===== 23 October Update =====

GOES-16 True Color images [click to play animation | MP4]

GOES-16 True Color RGB images [click to play animation | MP4]

GOES-16 True Color RGB images created using Geo2Grid (above) revealed the light brown hue associated with smoke from the East Troublesome Fire, which was being transported eastward across the North Atlantic Ocean; Hurricane Epsilon can be seen southwest of the smoke pall. The bulk of this smoke pall was being transported along a cold frontal boundary (below).

GOES-16 CIMSS Natural Color RGB images [click to play animation | MP4]'

GOES-16 CIMSS Natural Color RGB images [click to play animation | MP4]

NUCAPS Sounding profiles surrounding Colorado’s East Troublesome Fire

October 21st, 2020 |

NOAA-20 NUCAPS Profiles over Colorado, at locations indicated, at ca. 1900 UTC on 21 October 2020 (click to enlarge)

The East Troublesome Fire in Colorado expanded greatly on 21 October (click here for more information), and produced pyrocumulus clouds.  NOAA-20 overflew the fire at around 1930 UTC (linked-to overpass map from this site) on 21 October, and NUCAPS profiles, shown above, diagnosed the stability of the mid- and upper-troposphere.  The toggle below between the NOAA-20 VIIRS Visible (0.64 µm) and Infrared (11.45 µm) imagery and NUCAPS Sounding availability points show the relationships between cloudiness and point color.

Suomi NPP Visible (0.64 µm) and Infrared (11.45 µm) imagery at 2015 UTC on 21 October 2020, as well as (NOAA-20) NUCAPS Sounding availability points at ~1900 UTC on 21 October (Click to enlarge)

Gridded NUCAPS fields, below, of 500-300 mb lapse rates show very weak stability in and around the fire location.  A fire-driven updrafts in the region would not find much in the way to impede its vertical development.

NUCAPS estimates of upper-tropospheric (500-300 mb) lapse rates at ca. 1900 UTC on 21 October 2020 (Click to enlarge)

NOAA-20 sounder observations of the atmosphere during a downslope event

October 17th, 2020 |

GOES-16 Band 10 (7.3 µm) “Low-level water vapor” infrared imagery, 0831 – 1316 UTC (Click to animate)

Low-level water vapor imagery, above, from early morning on 17 October 2020, shows the characteristics of strong low-level winds in the lee of the Colorado Rockies, namely a warm trench and herringbone-like structures that suggest turbulent flow. This region is near the Cameron Peak fire, a long-lived conflagration to the west of Fort Collins (previous blog posts on this event are here, here and here).

Shortwave infrared imagery, below, captures the regions of hottest fire activity, both with Cameron Peak and with the newer East Troublesome fire to its southwest. Clouds moving down from the north impede the satellite view of the fires at the end of the animation.

GOES-16 Band 7 (3.9 µm) shortwave infrared imagery, 0921 – 1241 UTC, with surface observation plots (Click to animate)


NOAA-20 overflies Colorado twice daily; do the NUCAPS soundings produced from radiances observed by the CrIS (Cross-track Infrared Sounder) and ATMS (Advanced Technology Microwave Sounder) instruments on board NOAA-20 detect atmospheric structures (i.e., inversions) that trap energy and accompany downslope wind events?  On 16 October, in the afternoon, NOAA-20 NUCAPS soundings, below, did not show inversions.

NOAA-20 NUCAPS Profiles at the locations indicated, at ~1900 UTC on 16 October 2020 (click to enlarge)

Similarly, NUCAPS profiles from the morning pass on 17 October, however, around 0900 UTC,  did not show mid-tropospheric inversions over eastern Colorado, over the High Plains.

NOAA-20 NUCAPS Profiles at the locations indicated, at ~0900 UTC on 17 October 2020 (click to enlarge)

Some NUCAPS profiles upstream of the Front Range of the Rockies, however, showed ample evidence of inversions, especially in a region over central Colorado.

NOAA-20 NUCAPS Profiles at the locations indicated, at ~0900 UTC on 17 October 2020 (click to enlarge)

The 7.3 µm infrared image (Band 10, low-level water vapor), below, has turbulent structure near the regions where inversions were detected by NUCAPS.

GOES-16 ABI Band 10 (7.3 µm) at 0931 UTC, 17 October 2020. The blue-circled region roughly corresponds to the region where NUCAPS profiles show a mid-tropospheric inversion consistent with downslope winds to the east (Click to enlarge)

A wind speed plot from the NCAR Mesa Lab in Boulder, below (source), shows the periodic strong and gusty winds on 17 October.

Wind speeds and gusts for the 24 hours ending 11:52 MDT (1652 UTC) on 17 October 2020 (Click to enlarge)

Use NUCAPS profiles to gauge the strength of the inversion that is associated with downslope events.

Thanks to Paul Schlatter, SOO at WFO BOU, for the idea for this blog post!

Cameron Peak Fire becomes the largest on record for Colorado

October 14th, 2020 |

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

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

1-minute Mesoscale Domain Sector GOES-16 (GOES-East) “Red” Visible (0.64 µm), Shortwave Infrared (3.9 µm), “Clean” Infrared Window (10.35 µm) and Fire Temperature Red-Green-Blue (RGB) images (above) showed diurnal changes in the Cameron Peak Fire in northern Colorado on 14 October 2020. Aided by strong westerly winds at the surface (with peak gusts in the 50-70 mph range), the fire’s thermal signature initially began to increase in areal coverage and spread rapidly eastward — however, following the passage of a cold front around 18 UTC, an influx of cooler air with higher relative humidity halted this eastward expansion of the fire (with the thermal signature then retreating westward and diminishing in size). By that evening, the fire’s total burned area had grown to 158,300 acres, making it Colorado’s largest wildfire on record. While there was some pyrocumulus development over the fire source region, this large and hot fire did not produce a pyrocumulonimbus cloud.

Another view of the fire using 5-minute imagery from GOES-16 provided quantitative products such as Fire Power, Fire Temperature and Fire Area (below) — these 3 products are components of the GOES Fire Detection and Characterization Algorithm (FDCA). Surface observations showed that during the morning hours smoke was restricting surface visibility to 3 miles at Fort Collins (KFNL) and 5 miles at Greeley (KGXY).

GOES-16 Fire Temperature (top left), Shortwave Infrared (3.9 µm, top right), Fire Power (bottom left) and Fire Area (bottom right) [click to play animation | MP4]

GOES-16 Fire Temperature (top left), Shortwave Infrared (3.9 µm, top right), Fire Power (bottom left) and Fire Area (bottom right) [click to play animation | MP4]

GOES-16 True Color Red-Green-Blue (RGB) images created using Geo2Grid (below) indicated that one portion of the Cameron Peak Fire smoke plume was transported eastward across parts of Nebraska and Iowa, with another part of the plume moving southeastward across Kansas.

GOES-16 True Color RGB images [click to play animation | MP4]

GOES-16 True Color RGB images [click to play animation | MP4]

A toggle between Terra MODIS True Color and False Color RGB images on 14 October from the MODIS Today site (below) showed the  Cameron Peak Fire smoke plume as well as its large burn scar (shades of red).

Terra MODIS True Color and False Color RGB images on 14 October [click to enlarge]

Terra MODIS True Color and False Color RGB images on 14 October [click to enlarge]

In a comparison of MODIS False Color RGB images from Aqua on 13 October and Terra on 14 October (below) the growth of the Cameron Peak Fire along its southeast flank was evident — and several other large fire burn scars were evident across Colorado and southern Wyoming.

MODIS False Color RGB images from Aqua (13 October) and Terra (14 October) [click to enlarge]

MODIS False Color RGB images from Aqua (13 October) and Terra (14 October) [click to enlarge]

Additional aspects of this fire and its environment are discussed here.