11 de março de 2010

Surpresas...

Wunder Blog : Weather Underground: "The unnamed South Atlantic tropical/subtropical cyclone (90Q) off the coast of Brazil continues to spin slowly out to sea, and is not a threat to any land areas. The storm, just the 7th tropical or subtropical cyclone on record in the South Atlantic, 


Morning visible satellite image of the Brazilian unnamed tropical/subtropical storm

[...] When compared to similar systems that have developed in the North Atlantic that have been named, I definitely think today's storm deserves a name. [...] South Atlantic tropical storm history Brazil has had only one landfalling tropical cyclone in its history, Cyclone Catarina of March 2004. Catarina is one of only six known tropical or subtropical cyclones to form in the South Atlantic, and the only one to reach hurricane strength. Today's storm is probably the fourth strongest tropical/subtropical storm on record in the South Atlantic, behind Hurricane Catarina and an unnamed February 2006 storm that may have attained wind speeds of 65 mph, and a subtropical storm that brought heavy flooding to the coast of Uruguay in January 2009.. 

Tropical cyclones rarely form in the South Atlantic Ocean, due to strong upper-level wind shear, cool water temperatures, and the lack of an initial disturbance to get things spinning (no African waves or Intertropical Convergence Zone exist in the proper locations in the South Atlantic to help spawn tropical storms). Today's storm is located close to where Catarina formed. Climate change and South Atlantic storms It is uncertain whether climate change may cause an increase in South Atlantic tropical storms in the future. While today's storm formed over waters that were about 1°C above average in temperature, Catarina in 2004 formed over waters that were 0.5°C cooler than average. Sea surface temperature is not the main limiting factor inhibiting these storms, wind shear is. How climate change might change wind shear over South America has not been well-studied."

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