September 11, 2009
NASA Microwave Image Sees Eyewall Opening In Hurricane Linda
Linda managed to power up to hurricane status at 11 p.m. EDT Wednesday night (September 9), and she's running into cooler waters and wind shear, so she's not expected to hold that strength through tomorrow. Microwave imagery from NASA's Aqua satellite revealed a 10 percent opening in her eyewall and that's a clue that the storm can weaken.
At 11 a.m. EDT on September 10, Linda had maximum sustained winds near 85 mph and weakening is expected. Her hurricane force winds only extend to 25 miles out from the center, while tropical storm force winds extend out 140 miles from the center. She's moving north-northwest near 9 mph, and expected to slow a little in the next day or two. Minimum central pressure is 985 millibars. The center of hurricane Linda was located near latitude 18.4 north and longitude 130.1 west or about 1,340 miles west of the southern tip of Baja California.
The National Hurricane Center (NHC) uses all kinds of satellite imagery to enhance their tropical cyclone forecasts, and they looked at data from NASA's Aqua satellite and NOAA's GOES-11 satellite to see that Linda is poised for weakening. One sign of weakening came from GOES-11 infrared images taken from 11 p.m. EDT last night that indicated Linda's eye had disappeared.
Microwave images are created when data from NASA's Aqua satellite Atmospheric Infrared Sounder (AIRS) and Advanced Microwave Sounding Unit (AMSU) instruments are combined. These microwave images indicate where there is precipitation or ice in the cloud tops and the latest microwave image revealed Linda had cold, high thunderstorms.
This morning at 11 a.m. EDT, the NHC said "enhanced BD-curve infrared imagery and an Aqua-1 AMSR-E color composite microwave overpass suggest that Linda has strengthened some this morning."
The NHC discussion said, "Subsequent microwave imagery depicted a partial eyewall that was open over the southern semicircle. The overall cloud pattern has become slightly less organized in appearance and elongated from south to north...indicative of southerly or south-southwesterly [wind] shear." The microwave data, such as that from Aqua, indicated Linda's center is a little south and west of where it appears to be on geostationary images.
Linda is forecast to move into an environment with westerly wind shear between 23-28 mph and sea surface temperatures below 75F. Tropical cyclones need warm sea surface temperatures of at least 80F to maintain strength.
Text credit: Rob Gutro, NASA/Goddard Space Flight Center
Image Caption: NASA's Aqua satellite AIRS and AMSU instrument data created a microwave image of Hurricane Linda on September 10 at 6:41 a.m. EDT. The cold areas in this image (yellow-green) indicate where there is precipitation or ice in the cloud tops. The microwave image suggests cold, high thunderstorms, and a partial opening in her eyewall. Credit: NASA/JPL, Ed Olsen