NASA's TRMM satellite sees wide-eyed Hurricane Bill strengthening

August 18, 2009

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TRMM captured Hurricane Bill's heavy rainfall on Aug. 17 at 10:25 p.m. EDT. The yellow, green and red areas indicate rainfall between .78 to 1.57 inches per hour. Red areas are considered moderate rainfall. Credit: NASA, Hal Pierce

The TRMM satellite noticed a wide-eyed Hurricane Bill's rainfall is intensifying indicating he's getting stronger. Satellite images have also shown Bill's eye is widening.

NASA and the Japanese Space Agency's Tropical Rainfall Measuring Mission (TRMM) satellite flew over the center of Hurricane Bill on August 18, 2009 at 0225 UTC (August 17 at 10:25 p.m. EDT) capturing rainfall data.

TRMM rainfall images are false-colored with yellow, green and red areas, which indicate rainfall between 20 and 40 millimeters (.78 to 1.57 inches) per hour. Red areas are considered moderate rainfall.

The TRMM rainfall analysis from the TRMM Microwave Imager (TMI) and Precipitation Radar (PR) instruments reveal that hurricane Bill has an eye. This feature isn't apparent on the TRMM Infrared image (VIRS) but is evidence of Bill becoming a stronger category two hurricane with wind speeds increasing to about 85 knots (~98 miles per hour). In fact, satellite imagery shows that Bill's eye is quite large, between 35-45 nautical miles in diameter!

At 11 a.m. EDT, Hurricane Bill had maximum sustained winds near 105 mph, making him a Category Two on the Saffir-Simpson Scale. He is expected to strengthen into a Category Three hurricane, a major hurricane, with winds in excess of 110 mph. Bill was centered about 705 miles east of the Leeward Islands, near 15.9 north and 51.2 west. He was heading west-northwest near 16 mph with a minimum central pressure of 963 millibars.

Interests in the Leeward Islands should monitor Bill's progress, as his track is currently expected to remain at sea and sweep past them and head in a northwesterly direction over the next two days.

Source: NASA/Goddard Space Flight Center