NASA Satellites Eyeing 4 Tropical Systems Around the World For Possible Development

There are four low pressure areas in the tropics today that NASA satellites are all keeping an eye on for possible development. They are Systems 90S, 91S and 99S in the Southern Pacific, and System 93B in the Northern Indian Ocean. Despite a poor chance for development in all of them, one has triggered warnings in northern Australia because of its proximity to land.

NASA and the Japanese Space Agency manage the Tropical Rainfall Measuring Mission or TRMM satellite and TRMM passed over two of those four systems today. TRMM captured light to moderate rainfall in the low pressure area called "System 90S" on March 30 at 01:49 UTC. Rainfall rates were between 5 and 20 millimeters (0.2 and 0.8 inches) per hour within the storm. System 90S is located 500 miles north-northwest of Port Hedland, Australia, near 12.0 South latitude and 116.0 East longitude.

Infrared satellite imagery from the Atmospheric Infrared Sounder (AIRS) instrument aboard NASA's Aqua satellite revealed that the low has consolidated during the morning hours, while the Advanced Microwave Scanning Radiometer-E instrument showed deep convection on the north and south sides of the center of circulation. Despite these developments atmospheric dynamics are not currently favorable, so the Joint Typhoon Warning Center currently gives this low a poor chance for development.

The second tropical low pressure area NASA satellites are watching is also 500 miles away from land, and that's System 99S. System 99S is 500 miles north of the Cocos Islands today, near 9.8 South and 99.4 East. The TRMM satellite measured rainfall rates between 5 and 20 millimeters (0.2 and 0.8 inches) per hour within the System 99S early today. The AIRS infrared imagery captured from NASA's Aqua satellite shows that areas of deep convection exist on all sides of the low pressure center, but it's not uniform. Vertical wind shear is currently light and sea surface temperatures are warm enough to support development, however, the chance that it will develop into a tropical storm in the next 24 hours is poor. As the week progresses, perhaps the chance will improve with the environmental conditions.

The third tropical low pressure area isn't a tropical storm but it has triggered a watch for Australia's Northern Territories. Because of System 91S' location, about 200 miles northeast of Darwin, Australia (near 10.0 South and 133.1 East), a tropical cyclone Watch has been issued for the coastal communities between Cape Hotham, Port Keats, including Darwin and the Tiwi Islands. The Tiwi Islands include Melville and Bathurst Islands and are part of Australia's Northern Territory, 25 miles (40 km) north of Darwin where the Arafura Sea joins the Timor Sea. In addition, a Strong Wind Warning has been issued from Milingimbi to Troughton Island.

System 91S is expected to move in a southwesterly direction over the next several days and track over Snake Bay, Mellville Island and Cape Fourcroy, Bathurst Island.

NASA AIRS infrared imagery revealed today that the convection (rapidly rising air that produces the thunderstorms that power a tropical cyclone) are intensifying and expanding around System 91S' center. The convection, however appears disorganized in the low and the maximum sustained winds are between 15 and 20 knots (17-23 mph/27-37 kmh). The chance for development into a tropical storm in the next 24 hours remains poor, but the areas under the watch may feel System 91S' rains and some gusty winds.

The fourth area is in the northern hemisphere and in a different ocean. Tropical low 93B is located in the Northern Indian Ocean. Last night it was only 50 miles north of Phuket, Thailand near 9.0 North latitude and 98.7 East longitude. However, today, infrared satellite imagery from NASA's AIRS instrument showed that the low level circulation center has drifted inland. When a low is inland, its center of circulation is cut off from the warm waters that power the tropical cyclone. Because of weak steering winds, however, the low may move back seaward and redevelop in the warm waters offshore.

Currently the system's maximum sustained winds are between 15 and 20 knots (17-23 mph/27-37 kmh). The chance for development into a tropical storm in the next 24 hours remains poor, but coastal Thailand are already experiencing rains and some gusty winds from System 93B.

NASA's TRMM and Aqua satellites continue to provide data to forecasters who are keeping a watchful eye on all of these tropical low pressure areas.

Text Credit: Rob Gutro, NASA's Goddard Space Flight Center, Greenbelt, Md.