April 2007: A month of Northern Hemisphere water vapor images

April 30th, 2007

April 2007 water vapor images (QuickTime animation)

An animation of 3-hourly water vapor channel image composites from AWIPS during the entire month of April 2007 (25.5 MB QuickTime animation; 1280×1024 screen resolution required) shows the diverse variety of synoptic scale features that affected the Northern Hemisphere during that particular month.

Day 15 of Georgia’s “Sweat Farm Road” Fire

April 30th, 2007

GOES-12 visible images

The Sweat Farm Road / Big Turnaround fire complex (that started on 16 April 2007) has become the largest wildfire in Georgia history, burning over 472,000 acres so far. A series of daily (21:45 UTC) GOES-12 visible images (above) shows that the smoke plume drifted in different directions on various days due to shifting winds. A similar series of daily (21:45 UTC) GOES-12 3.9µm IR images (below) indicated that this was also a very hot fire (darker pixels = hotter brightness temperatures) — on many days the IR images revealed a saturation of the GOES-12 shortwave IR detectors (causing the temperature of the fire pixels to “roll-over” and be displayed as “cold” white pixels). The fire appeared to diminish somewhat on 27 April (note the smaller smoke plume and less intense fire hot spot on that day), but then it intensified the following day (and another new fire started just to the northwest).

GOES-12 3.9µm IR images

A 3-channel red/green/blue (RGB) composite image using the Terra MODIS channels 07, 02, and 01 (below) shows the large size of the resulting burn scar that covered a significant portion of the southern half of Ware county Georgia on 30 April. The active fires that were still burning on that day were evident by the red-colored “hot spots” along the southeastern edge of the burn scar — the leading edge of the active fires had moved southward into extreme northern Charlton county. The new fire that started just to the northwest (in Atkinson county) a day earlier was also exhibiting a pronounced hot spot and smoke plume.

MODIS false color image

Algae blooms off the California coast

April 27th, 2007

MODIS true color image (San Francisco sector)

According to news reports, algae blooms off the coast of California have been producing toxic levels of domoic acid that have recently killed large numbers of birds, sea lions, and dolphins. MODIS true color images centered over San Francisco, California (above; Java animation) show the presence of chlorophyll-containing phytoplankton (light blue-green color) along the immediate coastal waters during the 23 March to 24 April 2007 period.

Fatal tornado at Eagle Pass, Texas

April 25th, 2007

GOES-12 10.7µm IR  image

Severe convection developed ahead of a frontal boundary that was moving southward across the Rio Grande Valley region late in the day on 24 April 2007. GOES-12 was in Rapid Scan Operations, providing images at 5-minute intervals during much of the event; 10.7 µm InfraRed (IR) images (above; Java animation) showed that these supercells began to exhibit an “enhanced-v” signature about 30 minutes prior to the initial SPC storm reports (although the storm could very well have been producing severe weather before the time of the SPC reports, while it was still over Mexico). This storm produced large hail (up to 2.75 inches in diameter), strong winds (up to 76 mph), and the EF-3 tornado that killed 10 and injured 120 persons in the Eagle Pass, Texas / Piedras Negras, Mexico area.

NOAA-16 / GOES-12 IR comparison

A view of the storm with the 1-km resolution IR image from the polar orbiting NOAA-16 satellite revealed a striking “warm trench” signature surrounding the most intense overshooting top (above). You can get a sense that such a “trench” can surround an overshooting top by examining astronaut photography of thunderstorms taken from the space shuttle (image courtesy of Earth Sciences and Image Analysis Laboratory, NASA Johnson Space Center). The anvil top temperatures were as cold as -67º C on the GOES-12 IR image, which corresponded to the tropopause temperature near the 141 mb pressure level (14.3 km / 47,000 ft altitude) on the Del Rio, Texas rawinsonde report — however, the cloud top temperatures were significantly colder (-78º C) on the NOAA-16 IR image. In addition, a false-color composite using NOAA-16 AVHRR visible channels 01 and 02 along with IR channel 04 (below) shows a well-defined anvil-top cirrus plume streaming northeastward from the primary overshooting top region; this anvil plume was a very persistent feature on the GOES-12 visible imagery (Java animation).

NOAA-16 channels 01, 02, 04 RGB image