`The genesis of two category-five hurricanes (Katrina and Rita) in a row over the Gulf of Mexico is an unprecedented and troubling occurrence. But for most tropical meteorologists the truly astonishing “storm of the decade” took place in March 2004. Hurricane Catarina — so named because it made landfall in the southern Brazilian state of Santa Catarina — was the first recorded south Atlantic hurricane in history.
Textbook orthodoxy had long excluded the possibility of such an event; sea temperatures, experts claimed, were too low and wind shear too powerful to allow tropical depressions to evolve into cyclones south of the Atlantic Equator. Indeed, forecasters rubbed their eyes in disbelief as weather satellites down-linked the first images of a classical whirling disc with a well-formed eye in these forbidden latitudes.
In a series of recent meetings and publications, researchers have debated the origin and significance of Catarina. A crucial question is this: Was Catarina simply a rare event at the outlying edge of the normal bell curve of South Atlantic weather — just as, for example, Joe DiMaggio’s incredible 56-game hitting streak in 1941 represented an extreme probability in baseball (an analogy made famous by Stephen Jay Gould) — or was Catarina a “threshold” event, signaling some fundamental and abrupt change of state in the planet’s climate system?’