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Subject: G6) Why doesn't the South Atlantic Ocean experience
tropical cyclones?
Contributed by Chris Landsea
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.
In addition, the US OAR has documented
the occurrence of a strong tropical depression/weak tropical storm
that formed off the coast of Congo in mid-April 1991
(McAdie and Rappaport (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.
Penn State University write up on the South Atlantic hurricane
Last updated July 13, 2005
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