90Q: A Curious Short-Lived “Tropical” Cyclone in the Southern Atlantic

Tropical cyclones typically don’t form in the Southern Atlantic because the waters are usually too cool. However, forecasters at the Naval Research Laboratory noted that a low pressure system off the coast of Brazil appeared to have tropical storm-force winds yesterday.

On Wednesday, March 10 at 1400 UTC (9:00 a.m. ET) “System 90Q” was located near 29.8 degrees South latitude and 48.2 degrees West longitude, about 180 miles east of Puerto Alegre, Brazil. The Naval Research Laboratory said on March 10 the system had maximum sustained winds near 39 mph (35 knots) but has weakened today below the tropical storm-force winds threshold.

The Geostationary Operational Environmental Satellite, GOES-12 captured a visible image of System 90Q at 14:45 UTC (9:45 a.m. ET) on March 11, and it appeared as a small circular area of clouds off the Brazilian coast. GOES is operated by the National Oceanic and Atmospheric Administration, and NASA’s GOES Project, located at NASA’s Goddard Space Flight Center, Greenbelt, Md. creates some of the GOES satellite images.

System 90Q continues to move away from the Brazilian coast and is expected to be absorbed in a mid-latitude cold front in the next couple of days.

Low Strengthens Into Hubert, Making Landfall in Madagascar

The low that forecasters were watching for development yesterday, March 9, strengthened into Tropical Storm Hubert, and is already making landfall in eastern Madagascar.

The Atmospheric Infrared Sounder (AIRS) instrument on NASA’s Aqua satellite captured Tropical Storm Hubert’s cold thunderstorm cloud tops on March 10 at 5:11 a.m. ET as the western edge of the storm was already raining on eastern Madagascar. The infrared imagery showed two areas where convection was strong in Hubert: the northeastern and southern quadrants of the storm. It is in those two areas that the highest, coldest thunderstorm tops were revealed by AIRS infrared imagery. Those thunderstorm cloud tops were as cold as -63 Fahrenheit!

Hubert has maximum sustained winds near 39 mph (35 knots) and is moving west-southwest near 6 mph (5 knots). At 10 a.m. ET (1500 UTC) on March 10, Hubert was located about 160 nautical miles southeast of the capital city of Antananarivo, Madagascar near 20.9 South and 48.8 East.

As Hubert continues moving inland over the next two days, forecasts for the capital city and other areas in south central Madagascar will continue to experience periods of moderate to heavy rainfall, and gusty winds.

Animated multispectral satellite imagery showed a loss of central convection as Hubert’s center moves closer to a landfall. Once Hubert’s center is over land, forecasters expect Hubert will quickly fall below tropical storm strength.