Hurricane Season 2011: System 98S (Southern Indian Ocean)

NASA Satellite Spies Cold Cloudtops in System 98S That Hint at Tropical Development

NASA's Aqua satellite is already seeing the potential in a tropical low pressure area to blossom into a tropical cyclone through its very cold cloud top temperatures.

A low pressure system known as System 98S is currently moving over the northern coast of Western Australia appears to have a good chance for developing into a tropical cyclone later this week once it slides into the warm waters of the Southern Indian Ocean.

On Monday, January 24, 2011 EST, the low was nearing Kuri Bay, located on the northern coast of Western Australia. It is forecast to continue moving southwest and skip over water along the northern coast as it heads toward Beagle Bay, Derby and Broome will be affected by the low's outer rains and winds as it continues tracking southwest.

A Cyclone Warning is current for coastal and island communities from Kuri Bay to Wallal. A Cyclone Watch is current for coastal and island communities from Wallal to Exmouth.

NASA's Aqua satellite passed over System 98S on January 24 at 05:17 UTC (12:17 a.m. EST) and the Atmospheric Infrared Sounder (AIRS) instrument captured an infrared image of its cloud top temperatures. The coldest cloud tops are as cold as or colder than -63 Fahrenheit (-53 Celsius) and indicate the strongest thunderstorms and areas of likely heavy rainfall. Those coldest clouds were mostly over the Southern Indian Ocean; however, some were over Wyndham and farther to the northeast.

Forecasters at the Australian Bureau of Meteorology noted that System 98S is close to the west Kimberley coast and if it moves over open waters it could intensify into a tropical cyclone by Tuesday evening local time. That would mean heavy rains and gusty winds for the west Kimberley coast. Areas from Kuri Bay southwest to Beagle Bay are currently in the path of this low. That also includes Leveque, and Cockatoo Island.

At 1200 UTC (7 a.m. EST) January 24, System 98S had maximum sustained winds near 25 knots (29 mph/46) per hour. It was located near 14.7 South latitude and 126.1 East longitude approximately 305 nm west-southwest of Darwin, Australia. System 98S was moving west-southwest near 6 knots (7 mph/11 km/hr).

Surface observations at Truscott indicated that pressure had fallen by 4 millibars, indicating strengthening despite the low's center being over land. Southwest of the low-level center, near Doongan, the pressure was reported at 999 millibars, and the Joint Typhoon Warning Center noted that that suggests the low-level center is drifting southwestward along the coast.

System 98S is forecast to move over open waters tonight, where it is expected to strengthen.

Text Credit: Rob Gutro

NASA Goddard Space Flight Center, Greenbelt, MD
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