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; Read More
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.
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Severe convection developed ahead of a frontal boundary that was moving southward across the Rio Grande Valley late in the day on 24 April 2007. GOES-12 was in Rapid Scan Operations,... Read More
Severe convection developed ahead of a frontal boundary that was moving southward across the Rio Grande Valley 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.
A view of the storm with the 1-km resolution IR image from the polar orbiting NOAA-16 satellite revealed a “warm trench” signature surrounding the most intense overshooting top (above). You can get a sense that such a trench feature 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 (at an altitude of 14.3 km / 47,000 ft) on the Del Rio, Texas rawinsonde report — however, the overshooting top temperatures were significantly colder (-78º C) on the NOAA-16 IR image. In addition, a false-color RGB composite using NOAA-16 AVHRR visible channels 1 and 2 along with IR channel 4 (below) showed a well-defined above-anvil cirrus plume streaming northeastward from the primary overshooting top region; this anvil plume was also a persistent feature on GOES-12 visible images (animated GIF | MP4).
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An intense upper-tropospheric cutoff low was moving across the southern Rocky Mountain region on 24 April 2007, which was very evident on GOES-12 water vapor imagery (QuickTime animation). An AWIPS image of the 17... Read More
An intense upper-tropospheric cutoff low was moving across the southern Rocky Mountain region on 24 April 2007, which was very evident on GOES-12 water vapor imagery (QuickTime animation). An AWIPS image of the 17 UTC operational “GOES high density winds” overlaid on a 17:10 UTC water vapor image (above) did not adequately resolve the closed circulation; in contrast, the CIMSS “GOES mesoscale winds” (or “Atmospheric Motion Vectors”) generated at 16:15 UTC (below) did show the closed circulation of the upper low over eastern Colorado. These mesoscale winds are part of a suite of products available on the Satellite-based Nowcasting and Aviation Application Program (SNAAP) site.
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No…just a weak cyclonic vortex off the Atlantic coast of Florida that just happens to look like a tropical cyclone with an eye! GOES-12 visible imagery (above; Java animation) shows the cloud swirl as it developed what appeared to be an “eye” on... Read More
No…just a weak cyclonic vortex off the Atlantic coast of Florida that just happens to look like a tropical cyclone with an eye! GOES-12 visible imagery (above; Java animation) shows the cloud swirl as it developed what appeared to be an “eye” on 20 April 2007. While this vortex was responsible for some weak banded offshore rain features (radar reflectivity image), the GOES-12 10.7 µm IR brightness temperatures were still very warm (around 0º C), indicating a lack of deep convection. The vortex existed in a high-shear environment — around 90 knots on the CIMSS wind shear product (below) — which was not favorable for tropical cyclone development. In addition, the MODIS sea surface temperatures in that region were still below the 80º F (26.7º C) threshold generally considered necessary for tropical cyclone genesis, and GOES sounder total precipitable water values were only in the 20-30 mm (0.79-1.18 inch) range.
The history of this particular swirl is rather interesting. A Weather Channel Blog posting discussed a possible Mesoscale Convective Vortex (MCV) origin; if we follow satellite imagery back in time for a day or two, the development of this feature appears to have been tied to a fairly large mid/upper tropospheric cyclone that was just south of the Great Lakes on 18 April (QuickTime animations: GOES water vapor | GOES IR). A potential vorticity (PV) anomaly associated with the cyclone shows up as a local maximum of GOES Sounder total column ozone (light green to red enhancement on this QuickTime animation); a GFS model cross section through the region of the swirl at 18 UTC on 20 April (below) suggests that a PV “tail” lagging behind the main PV anomaly farther offshore may have played a role in helping to spin up the swirl.
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