Meteosat-7 IR images (click to play animation)

Super Cylone 02A (“Gonu”) intensified rapidly in the Arabian Sea on 03-04 June 2007. EUMETSAT Meteosat-7 InfraRed imagery (above; animated GIF) showed very cold cloud-top IR brightness temperature values (-80º to -88º C, violet to purple enhancement) in the eyewall region during much of the 2-day period. A distinct eye was apparent on the Meteosat-7 IR images, as well as on the Meteosat-7 visible images on 04 June (animated GIF).

An overpass of the NOAA-17 satellite occurred at 17:33 UTC on 04 June; the IR image (below) depicted a detailed radial “banded structure” to the cold brightness temperature field, with a minimum temperature of -89º C (darker purple enhancement). Also note the area of concentric gravity waves south of the eye (within the gray-to-white enhanced area of -75º to -79º C brightness temperatures).

NOAA-17 IR image

The CIMSS Advanced Dvorak Technique is a satellite-based method of estimating tropical cyclone intensity; the ADT plot (below) indicates that Gonu intensified very rapidly from late in the day on 03 June (day 2007154) to early in the day on 04 June (day 2007155), reaching Category 5 intensity (with 140 knot wind speeds). This was the first tropical cyclone of Category 5 strength on record in the Arabian Sea.

Gonu ADT plot

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Tropical Storm Barry formed in the eastern Gulf of Mexico on 01 June 2007 (the first official day of the Atlantic hurricane season). An AWIPS image of the GOES-12 10.7µm IR channel (above; Java animation) showed that some bursts of convection were developing just north of the center of Barry, with cold IR brightness temperature values of -70º to -80º C (black to white enhancement). The tropical cyclone was embedded in an environment of strong southwesterly wind shear in the middle levels and upper levels of the atmosphere, which was not conducive to further strengthening of Barry.

An AWIPS 4-panel comparison of DMSP SSM/I and POES AMSU imagery (below) revealed that rainfall rates near the center of TS Barry were in the 25-35 mm (1.0-1.4 inch) per hour range (orange to red enhancement, upper panels), while total precipitable water values were increasing to 50-60 mm or 2.0-2.4 inches (violet to purple enhancement, lower panels) in the environment surrounding the storm over the eastern Gulf of Mexico. Note that the times displayed on the AWIPS DMSP and POES images do not necessarily correspond to the actual time of the satellite overpass for the particular region being viewed.

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Hot spots on GOES-12 3.9µm and MODIS 3.7µm IR imagery (above) indicated the presence of several wildfires near the northwestern shoreline of Lake Okeechobee in southern Florida on 30 May 2007. The fires were hot enough to saturate the shortwave IR detectors on GOES-12, causing the hottest brightness temperatures (normally appearing as black pixels) to “roll over” and show up as “cold” (white) pixels. An Aqua MODIS true color image (below) showed a smoke plume extending westward from the fires, with the smoke reaching the Gulf Coast of Florida. That region continued to experience extreme drought conditions — in fact, the water levels for the lake set an all time record low (note how much the lake water had receded from the southern, western, and northwestern portion of Okeechobee in the MODIS true color image).

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An AWIPS image of the GOES 10.7µm InfraRed (IR) channel (above) shows Tropical Depression Alvin (left) and Tropical Storm Barbara (right) on 30 May 2007 — both disturbances were located near the Intertropical Convergence Zone (ITCZ) over the Eastern Pacific Ocean. The morning NHC discussion pointed out that only twice before (in 1956 and 1984) have there been two named Eastern Pacific basin storms in the month of May. An animation of GOES-12 IR imagery with a different color enhancement (below) indicates that the cold cloud top temperatures (red to white enhancement) associated with Tropical Storm Barbara were increasing in areal coverage during the morning hours.

The NHC discussion also made reference to the CIMSS Advanced Dvorak Technique or ADT (below) in their decision to upgrade Tropical Depression Barbara to a Tropical Storm.

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