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.
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/GSF.
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'.
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.
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.