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Day 14 of the Thomas Fire in Southern California

By Scott Bachmeier •

GOES-15 Shortwave Infrared (3.9 µm) images, with surface station identifiers plotted in yellow [click to play MP4 animation]

05-17 December GOES-15 Shortwave Infrared (3.9 µm) images, with surface station identifiers plotted in yellow and State Highway 101 plotted in cyan [click to play MP4 animation]

The Thomas Fire (InciWeb | Wikipedia) began to burn around 0226 UTC on 05 December 2017 (or 6:26 PM Pacific time on 04 December). By 17 December, the fire had burned 270,000 acres — the third largest wildfire on record in California — and caused 1 fatality. An animation of GOES-15 (GOES-West) Shortwave Infrared (3.9 µm) images (above) showed the evolution of the thermal signature (or “hot spots”, as depicted by darker black to yellow to red pixels) during the 0200 UTC 05 December to 0215 UTC 18 December time period. Besides the largest Thomas Fire, other smaller and more short-lived fires could also be seen — especially early in the period, when the Santa Ana winds were strongest (05-07 December blog post). Thick clouds moving over the region later in the period either attenuated or completely masked the thermal signatures, even though the fire was ongoing.

GOES-16 began transmitting imagery (from its GOES-East position at 75.2º W) at 1630 UTC on 14 December — a comparison of GOES-15 and GOES-16 Shortwave Infrared (3.9 µm) during the 14-17 December period (below) showed that in spite of the larger GOES-16 satellite view angle (62.6º, vs 43.2º for GOES-15), the improved spatial resolution (2 km vs 4 km at satellite sub-point) and improved temporal resolution (images every 5 minutes, with no 30-minute gaps due to Full Disk scans) provided a more accurate depiction of the fire trends and intensities.

GOES-15 (left) and GOES-16 (right) Shortwave Infrared (3.9 µm) images [click to play MP4 animation]

GOES-15 (left) and GOES-16 (right) Shortwave Infrared (3.9 µm) images [click to play MP4 animation]

In a comparison of 250-meter resolution Terra MODIS true-color and false-color Red-Green-Blue (RGB) images (source) at 1853 UTC on 17 December (below), minimal amounts of smoke and a lack of clouds allowed a good view of the large Thomas Fire burn scar (darker shades of reddish-brown) on the false-color image.

Terra MODIS true-color and false-color RGB images on 17 December [click to enlarge]

Terra MODIS true-color and false-color RGB images on 17 December [click to enlarge]

During the first full day of the fires on 05 December, a toggle between comparable Aqua MODIS true-color and false-color images (source) revealed very thick smoke plumes drifting southwestward over the adjacent offshore waters of the Pacific Ocean (below).

Aqua MODIS true-color and false-color images, 05 December [click to enlarge]

Aqua MODIS true-color and false-color RGB images on 05 December [click to enlarge]

A toggle between 05 December Aqua MODIS and 17 December Terra MODIS false-color images (below) showed the northward and northwestward growth of the Thomas Fire burn scar.

Aqua MODIS (05 December) and Terra MODIS (17 December) false-color RGB images [click to enlarge]

Aqua MODIS (05 December) and Terra MODIS (17 December) false-color RGB images [click to enlarge]

Categories: Aqua, Fire detection, GOES-15, GOES-16, MODIS, Red-Green-Blue (RGB) images, Terra