| South Atlantic Hurricane breaks all the
rules |
Pick up any text book on hurricanes and it will tell you that
the one place where hurricanes do not occur is the South Atlantic
Ocean. The atmosphere does not provide enough spin near the surface
to get them started and winds higher in the atmosphere tend to
shear off any that do make a start. Hence, it was with some amazement
that meteorologists watched the first ever recorded hurricane
develop off the coast of Brazil in the last week of March.
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Tropical cyclone Catarina off Southern Brazil, 26 March
2004. The first hurricane recorded in the South Atlantic.
Image courtesy of MODIS
Rapid Response Project at NASA/GSFC.
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Initially the storm did not look much like a hurricane, but in
common with some of its counterparts which develop in the North
Atlantic Ocean, it acquired enough characteristics to convince
the majority of the world's tropical cyclone experts that it was
indeed a hurricane. It came ashore in the Brazilian state of Santa
Catarina on 28 March 2004 with winds, estimated by the US National
Hurricane Center, of near 90 m.p.h., causing much damage
to property and some loss of life. The Brazilian meteorologists
dubbed it 'Catarina'.
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Climate Change signal?
Climate change scientists, working in the Met
Office Hadley Centre,
recognised this as a feature they see in their climate model.
In a world made warmer by increased greenhouse gasses, their
model shows that this is one of the areas to watch in the
future as there may indeed be more tropical storms for the
South Atlantic.
The signal is not clear, however, as some aspects of the
model are not realistic and don't exactly match the current
storm, but the potential is there and the event is part
of the climate change jigsaw, which experts are piecing
together.
In the figure below, the red colours show where the climate
model is expecting an increase in storm activity. The crosses
highlight the track of the hurricane.
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Debate still continues as to the true nature of this cyclone
and why it should have developed in a region where no hurricane
activity has been observed in the past. However, one thing is
certain; 'Catarina' is set to become one of the most intensely
studied hurricanes in history.
More about tropical
cyclone forecasting at the Met Office
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