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Ketsana formed into a tropical depression several hundred miles east ofthe Philippines at 18:00 UTC on 18 October 2003 and continued to organizeinto a tropical storm. The Tropical Rainfall Measuring Mission (TRMM)satellite overflew Ketsana on the 19th and captured this first image (left) at22:23 UTC. At the time, Ketsana was a tropical storm with winds estimatedat 50 mph by the Joint Typhoon Warning Center. The TRMM image provides atop down view of Ketsana showing rainfall rates within the storm from theTRMM Precipitation Radar (PR) in the inner swath and the TRMM MicrowaveImager (TMI) in the outer swath overlaid on Infrared (IR) data from theTRMM Visible Infrared Scanner (VIRS). TRMM detected a large area ofintense rainfall along the southwest side of the storm’s large center(shown by the darker reds). The heat being released near the storm centerfrom the area of heavy precipitation allowed Ketsana to further developinto a typhoon.
The next image (right) was taken at 21:28 UTC on October 20th. Ketsana was now aCategory 1 storm with sustained winds estimated to be over 90 mph. Thethe storm appears better organized with a closed center that is muchsmaller in diameter. Moderate rain rates (green areas) surround the eyein concentric bands. The IR data indicates that Ketsana is a fairlysymmetrical storm and does not appear to be inhibited by wind shear.Thus, conditions remain favorable for further development. Fortunately,Ketsana is moving away from the Philippines towards the northeast and isnot an immediate threat to any appreciable land masses.
TRMM is a joint mission between NASA and the Japanese space agency NASDA.
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Images produced by Hal Pierce (SSAI/NASA GSFC) and caption by Steve Lang (SSAI/NASA GSFC).
