A wildfire started in the Fourmile Canyon area northwest of Boulder, Colorado on the morning of 06 September 2010 — and strong winds (gusting to around 45 mph) in the wake of a cold frontal passage helped the fire to spread very quickly to a size of about 3500 acres. Some homes and buildings were destroyed, a fewÂ evacuations were ordered, and there were a number of road closures in the area. AWIPS images of 4-km resolution GOES-13 3.9 Âµm shortwave IR data (above) showed the associated “hot spots” (black to red to yellow pixels) as the fire continued to grow during the day. Note the presence of very dry air over parts of the region –Â the dew point was as low as -17Âº F at Boulder, due to downsloping winds.

AWIPS images of 1-km resolution MODIS 0.65 Âµm visible, MODIS 3.7 Âµm shortwave IR, and MODIS 11.0 Âµm IR channel data (below) showed a more detailed view of the fire smoke plume and hot spots at 18:13 UTC (12:13 pm local time).

The MODIS Land Surface Temperature (LST) product (below) indicated LST values as high as 126.7ÂºÂ F (red color enhancement) at the source region of the fire. Note how the Land Surface temperatures were reduced significantly beneath the thick smoke plume, due to a reduction in the amount of solar heating — LST values were in the mid 60s to low 70s F (darker green color enhancement) under the smoke plume, in contrast to areas with LST values in the low to mid 90s F (darker orange color enhancement) in adjacent areas. The highest elevations of the Rocky Mountains had LST values as cold as the low 40s F (darker blue color enhancement).

A comparison of the 1-km resolution MODIS Normalized Difference Vegetation Index (NDVI) product on 05 September (the day before the fire) and 06 September (below) indicated that the fire was burning in an area with adequate fuels — NDVI values near the fire source region were in the 0.5 to 0.6 range on 05 September.

250-meter resolution MODIS true color Red/Green/Blue (RGB) images from the SSEC MODIS Today site (below) showed a very detailed view of the structure of the smoke plume.

By the end of the daylight hours, McIDAS images of GOES-13 0.63 Âµm visible channel data (below; also available as a QuickTime movie) indicated that strong winds aloft had blown the leading edge of the smoke plume as far northeastward as the Nebraska / Iowa border region. The GOES-13 satellite had been placed into Rapid Scan Operations (RSO) to monitor the landfall of Tropical Storm Hermine, so images were available as frequently as every 5-10 minutes.

The above iPhone image, looking northwest towards Boulder from the Davidson Mesa Open Space in Louisville, CO, was taken by Tom Davinroy about six hours after the fire started. There is also a time lapse video of the fire as it burned through the night.

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

Due to a favorable forward scattering geometry, early morning GOES-11 visible images on 07 September 2010 (above) revealed that the smoke had been transported as far northeastward as southern Wisconsin, northern Illinois, and Lower Michigan.

A comparison of the 250-meter resolution MODIS true color RGB image on 06 September with the MODIS true color and false color RGB images on 07 September (below) showed that there was a much smaller, more localized smoke plume on 07 September — and the burn scar (which appeared darker brown in color) was apparent on the 07 September false color image. At the edge of the burn scar, the brighter pink area seen on the false color image was a heat signature of the active fire that was still burning at that time.