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Why rare March tropical storm in Atlantic unlikely to develop

Tropical Storm Iba develops in a unique part of ocean

A satellite view of Tropical Storm Iba on March 25 east of Brazil.
A satellite view of Tropical Storm Iba on March 25 east of Brazil.

JACKSONVILLE, Fla. – A rare Tropical Storm that formed in the South Atlantic east of Rio De Janeiro is being tracked by the Brazil’s meteorological organization. 

The swirl of clouds is not forecast to become a hurricane but winds are estimated between 40 and 50 mph and any impacts from the storm will stay well away from South America.

Tropical storms in the South Atlantic are very rare. In fact, only one hurricane has formed in this region, and that was back in 2004.

High wind shear across the tropical south Atlantic is one reason keeping the Brazilian coast safe from hurricanes. Also, tropical waves that seed nascent storms do not travel westward like they do north of the equator in the Atlantic.

Together these features typically prevent tropical cyclones in the southern Atlantic. 

Hurricanes are not able to cross the equator because the wind circulation around the eye would fall apart due to Earth’s Coriolis force becoming negligible at the equator. 

It has been nine years since a pure tropical storm, Anita, formed near the coast of Brazil.

Warm water flows south along the coast of Brasil but tropical storms rarely develop in this area.
Warm water flows south along the coast of Brasil but tropical storms rarely develop in this area.

The upcoming seasonal hurricane prediction for the North Atlantic from The University of Colorado will be released on April 4.

While the outlook’s places emphasis on Pacific El Nino/La Nina patterns, the researchers typically do not make correlations between South Atlantic tropical cyclones and increased north Atlantic activity.


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