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.

Each summer, sandstorms lift millions of tons of dust from the Sahara, carrying plumes of it off the West Coast of Africa and over the Atlantic Ocean. Eric Wilcox, a researcher at NASA’s Goddard Space Flight Center, has been using data from NASA satellites to examine the impact such storms can have on rainfall patterns. Wilcox has a new paper about his findings in Geophysical Research Letters; Nature Geoscience also highlighted it in a recent issue. As a result, we sat down with Wilcox to discuss his new findings and some little-known details about dust.

Cyclone 17P Briefly Named Sarah, Then Fizzles

Cyclone 17P finally strengthened enough to get named Tropical Storm Sarah over the weekend, as it continued on a southern track toward the South Cook Islands. It didn’t hold together long however, as by Monday, March 1, the storm has dissipated.

Tropical Storm Sarah’s winds peaked around 39 mph (35 knots) on Saturday, February 27. Thirty-nine mph is the lowest maximum sustained wind speed a cyclone can have to be classified as a tropical storm. At 10 a.m. ET on Saturday, the Joint Typhoon Warning Center issued its final warning on the system.

It was about 555 miles east-southeast of Pago Pago, American Samoa at that time, near 17.4 South latitude and 162.5 East longitude. Sarah/17P was still moving at the slow pace it maintained the previous week, at 4 mph (3 knots). Sarah was generating 8-foot high waves on Saturday that affected the coasts of the South Cook Islands.

Low 17P Has a Good Chance for Tropical Reformation This Weekend

The Joint Typhoon Warning Center is the forecast center that issues advisories for tropical cyclones in the Southern Pacific Ocean, and they noted on February 26, “Available data does not justify issuance of numbered tropical cyclone warnings at this time” That may change over the weekend, as maximum sustained winds are near tropical depression strength, 34 mph (30 knots) and environmental factors are looking more favorably for further development.

17P’s center is near 16.3 degrees South latitude and 163.6 West longitude, that’s about 425 nautical miles east-southeast of Pago Pago. The system is crawling south-southwestward at 2 mph (2 knots).