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Subject: G6) Why doesn't the South Atlantic Ocean experience tropical cyclones?
Contributed by Chris Landsea (NHC)
What never ?? Well, hardly ever.
In March, 2004 a hurricane DID form in the South Atlantic Ocean and made landfall in Brazil. But this still leaves the question of why hurricanes are so rare in the South Atlantic. Though many people might speculate that the sea surface temperatures are too cold, the primary reasons that the South Atlantic Ocean gets few tropical cyclones are that the tropospheric (near surface to 200mb) vertical wind shear is much too strong and there is typically no inter-tropical convergence zone (ITCZ) over the ocean (Gray 1968). Without an ITCZ to provide synoptic vorticity and convergence (i.e. large scale spin and thunderstorm activity) as well as having strong wind shear, it becomes very difficult to nearly impossible to have genesis of tropical cyclones. Penn State University offers a write up on the South Atlantic hurricane here.
In addition, McAdie and Rappaport (1991) documented the occurrence of a strong tropical depression/weak tropical storm that formed off the coast of Congo in mid-April of 1991. This storm lasted about five days and drifted toward the west-southwest into the central South Atlantic. So far, there has not been a systematic study as to the conditions that accompanied this rare event.
Last updated July 13, 2005
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