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NASA Infrared Satellite Instrument Sees Tropical Storm Iggy Growing In Strength

January 27, 2012

The AIRS infrared instrument that flies on NASA’s Aqua satellite has been providing forecasters with the cloud top temperatures in the Southern Indian Ocean’s ninth tropical cyclone, which has officially been renamed Iggy. AIRS data showed that the area of strong thunderstorms around Iggy’s center has expanded in area over the last day.

The Atmospheric Infrared Sounder (AIRS) instrument provided an infrared snapshot of Iggy’s cloud top temperatures on January 26, 2012 at 0611 UTC (1:11 a.m. EST). The AIRS image showed a large and rounded area of high, cold clouds, around the entire center of circulation. The data also showed that strongest convection (rapidly rising air that condenses and forms the thunderstorms that make up the cyclone) is located slightly to the west of the center, because of easterly wind shear. The temperatures of those high cloud tops were colder than -63 Fahrenheit (-51.7 Celsius), which is a threshold scientists use to identify strong thunderstorms with heavy rainfall. This is an indication that Iggy will continue to strengthen.

The AIRS image also showed clouds to the southeast of Iggy that are associated with another low pressure area. That area of disturbed weather is over land and located south-southwest of Darwin.

Iggy is currently located in the Southern Indian Ocean, northwest of Western Australia. At 1500 UTC (10 a.m. EST), Tropical Cyclone Iggy was about 430 nautical miles (~495 miles/~796 km) northwest of Learmonth, Australia, near 16.8 South and 109.0 East. It was moving slowly to the southeast at 5 knots (~6 mph/~9 kph). Iggy’s maximum sustained winds are near 45 knots (~52 mph/~83 kph) and it is classified as a tropical storm. Those tropical-storm-force winds extend out to 110 miles (177 km) from the center.

Iggy’s approach has prompted the Australian Bureau of Meteorology to issue a cyclone and flood watch. Iggy is moving toward the Pilbara coast. The coastal communities between Whim Creek and Coral Bay will likely experience gusty winds and heavy rainfall on January 27 and 28. Rough surf is also expected along coastal areas including Christmas Island, the Kimberley and Pilbara coasts.

Iggy is forecast to continue strengthening as it moves southeast toward Western Australia. Sea surface temperatures along track are 28 to 29 degrees Celsius (~82 to ~84 Fahrenheit), which the Joint Typhoon Warning Center says is supportive of further development. It is expected to reach cyclone strength before moving to the south.

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