December 21, 2009
Tropical Storm David Forms and Romps in the Southern Indian Ocean
Hurricane Season 2009: Tropical Storm David (Southern Indian Ocean)
Tropical Storm David formed over the weekend and as a depression, has been romping around the open waters of the Southern Indian Ocean and will continue to do just that. David is located approximately 580 nautical miles west-southwest of Diego Garcia, near 11.3 degrees South and 63.8 degrees East.
David has been tracking in a westward direction, but it now changing course and moving east-southeast near 7 mph. David's maximum sustained winds are near 46 mph, and the storm may strengthen over the next couple of days.
Animated infrared satellite imagery, such as that using NASA's Atmospheric Infrared Sounder (AIRS) instrument on the Aqua satellite, indicates slight improvement in organization over the past 12 hours despite moderate northwesterly vertical wind shear. AIRS captured an infrared and visible image of David on December 21 at 09:17 UTC (4:17 a.m. ET) and noticed that David had some high thunderstorm tops indicating strong convection and strong thunderstorms with heavy rainfall. The cloud tops were as cold or colder than minus 63 degrees Fahrenheit!
On December 21 at 1504 UTC (10:04 ET) the Tropical Rainfall Measuring Mission (TRMM) satellite, a satellite managed by NASA and the Japanese Space Agency, flew over David to analyze the storm's rainfall. The image showed convective banding, that is, bands of thunderstorms, wrapping from the north of the storm into the south of the storm. Microwave imagery, however, such as that from NASA's Aqua satellite showed that David's low-level circulation is partially exposed, opening the storm up to wind shear, which could weaken it.
David is forecast to keep moving east-southeast for the next 72 hours and then turn southwestward while intensifying slightly. David poses no threat to land.
Rob Gutro, NASA's Goddard Space Flight Center