NASA sees Tropical Storm Pewa temporarily weakenAugust 20, 2013 in Earth / Earth Sciences
Tropical Storm Pewa weakened temporarily while facing adverse atmospheric conditions in the Northwestern Pacific, and NASA's Aqua satellite captured the storm in infrared light.
The Atmospheric Infrared Sounder or AIRS instrument aboard NASA's Aqua satellite captured an infrared image of Tropical Storm Pewa on Aug. 20 at 01:47 UTC/9:47 p.m. EDT, Aug. 19 as it weakened. The coldest cloud top temperatures and strongest storms were confined to a small area around the storm's center and in a band of thunderstorms northeast of the center. Cloud top temperatures in both of those areas were as cold as -63F/-52C. Infrared imagery since this AIRS image has shown that convection has deepened and thunderstorms have become stronger.
At 0900 UTC on Aug. 20, Pewa's maximum sustained winds dropped to 45 knots/51.7 mph/83.3 kph as it faced wind shear. By 1500 UTC/11 a.m. EDT, winds had strengthened to 50 knots/57.5 mph/92.6 kph. Forecasters at the Joint Typhoon Warning Center expect Pewa to strengthen into a typhoon later this week. Pewa was located near 17.5 north and 173.4 east, about 436 nautical miles east-southeast of Wake Island. Pewa is moving to the northwest at 13 knots/15 mph/24 kph and is expected to pass far to the north of Wake Island from Aug. 21 to 22.
Forecasters at the Joint Typhoon Warning Center noted that as Pewa moves through warm ocean waters, a decrease in vertical wind shear will happen over the next couple of days and that will allow for Pewa to strengthen to typhoon force.
Provided by NASA's Goddard Space Flight Center
"NASA sees Tropical Storm Pewa temporarily weaken" August 20, 2013 http://phys.org/news/2013-08-nasa-tropical-storm-pewa-temporarily.html