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44 Why doesn't the South Atlantic Ocean experience tropical cyclones?




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This article is from the Storms FAQ, by Chris Landsea landsea@aoml.noaa.gov with numerous contributions by others.

44 Why doesn't the South Atlantic Ocean experience tropical cyclones?

Though many people might speculate that the sea surface temperatures are
too cold, the primary reasons that the South Atlantic Ocean gets no 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.

However, in rare occasions it may be possible to have tropical cyclones
form in the South Atlantic. In McAdie and Rappaport (1991), the USA
National Hurricane Center documented the occurrence of a strong tropical
depression/weak tropical storm that formed off the coast of Congo in
mid-April 1991. The 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.

 

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