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Hurricane Season 2008: 06B (Indian Ocean)
Nov. 26, 2008

Southern India Visited by Tropical Cyclone 06B

AIRS image of Tropical Cyclone 06B in the Indian Ocean> Larger image
Credit: NASA JPL
Tropical Cyclone 06B formed very quickly during the overnight period of Nov. 25-26 and moved through the Palk Strait between Sri Lanka and India in the early morning hours. It started raining and bringing gusty winds to southeastern India on Nov. 25, and made landfall in southern India mid-day on Nov. 26.

On Nov. 26 at 9:00 Zulu Time (4:00 a.m. EST), Cyclone 06B was located near 10.3 degrees north latitude and 79.9 degrees east longitude. That's near the southeastern coast of India and about 225 nautical miles east of the city of Cochin, India (located on the southwest side of the peninsula). Its maximum sustained winds were near 55 knots (63 mph), and it was slowly moving northwest inland into southern India. Cyclone 06B is forecast to weaken rapidly as it continues on a northwestward inland track.

According to the Hindu newspaper on-line, in the city of Ramanathapuram on the southeast coast, the third stage cyclone warning flag was raised at the Pamban port, advising fishermen not to venture out to sea. The cyclone warning indicated that winds would be between 40-46 miles per hour. Winds and rains affected the city on Nov. 25, and was expected through Nov. 26 as Cyclone 06B moved slowly northwestward.

Some of the satellite data that forecasters use to determine if a storm will hold together, dissipate or strengthen are cloud temperatures. They look at data from the Atmospheric Infrared Sounder (AIRS) instrument that flies on NASA's Aqua satellite. When cloud temperatures get colder, it means that clouds are getting higher. Building clouds indicate a lot of "uplift" in the atmosphere and stronger thunderstorms. The data from AIRS is also used to create an accurate 3-D map of atmospheric temperature, water vapor and clouds, all of which are helpful to forecasters.

The infrared image, taken on Nov. 25 at 2:23 p.m. EST (19:23 UTC) shows a huge temperature difference between the tops of the clouds in a tropical cyclone and the warm ocean waters that power it. The lowest temperatures (in purple) are associated with high, cold cloud tops that make up the top of the storm. Those temperatures are as cold as or colder than 220 degrees Kelvin or minus 63 degrees Fahrenheit (F). The blue areas are around 240 degrees Kelvin, or minus 27F.

AIRS infrared signal doesn't penetrate through clouds, so where there are clear skies AIRS reads the infrared (heat) signal from the ocean and land surfaces, revealing warmer temperatures (colored in orange and red). The orange temperatures are 80F (300 degrees Kelvin) or greater (the darker they are, the warmer they are). Tropical cyclones need sea surface temperatures of 80F to strengthen and maintain their strength.

Text Credit: Rob Gutro (from JTWC reports)/NASA's Goddard Space Flight Center