Brazil Picking Up Pieces After Worst Tropical Storm. (Hurricane?)

RIO DE JANEIRO, Brazil (AP) - A day after a massive tropical storm battered the southern coast, Brazilians tended to victims and struggled to understand exactly what hit them. Civil defense officials said Monday the storm - dubbed Catarina by meteorologists - left at least three people dead, 38 injured and more than 2,000 people homeless.

Rescuers plucked two fishermen from the sea and found the body of another off Brazil's southern coast Monday.

Brazilian meteorologists, meanwhile, disputed assertions by U.S. weather experts that the storm was a hurricane.

U.S. officials said the storm, which struck land some 520 miles southwest of Rio de Janeiro packing sustained winds of more than 74 mph, appeared to be the first hurricane on record in the South Atlantic.

The U.S. National Hurricane Center in Miami estimated the storm was a full-fledged, Category I hurricane with central winds of 75-80 mph. A private U.S. forecasting company, AccuWeather, said it also considered the storm a hurricane. Some gusts reportedly hit 94 mph.

But Brazilians, who have long prided themselves as having a country free of hurricanes, were not convinced.

"The system that hit Santa Catarina this weekend was not a hurricane," Brazil's National Space Research Institute said in a statement Monday, arguing that it didn't behave like a hurricane.

"This system was totally different from anything we've ever seen here," said Laura Rodrigues, a meteorologist at the Santa Catarina state weather bureau. "It may be that it was neither a hurricane nor a subtropical cyclone, but rather something completely new."

Jack Beven, a specialist at the U.S. Hurricane Center, said all data point to a hurricane, but suggested that American and Brazilian officials "analyze the data a bit further" to see if they can reach a resolution.

Worst hit was Santa Catarina state, where 14 cities and towns remained without drinking water and 11 had no electricity Monday.

Santa Catarina Civil defense official Marcio Luis Alves said at least 1,990 people lost their homes and 9,590 were forced to flee. More than 30,000 houses across the state were damaged, and 280 were destroyed.

The storm also damaged 1,373 public buildings and private businesses, Alves said. Fifty were destroyed, including a hospital.

Alves said that meteorologists provided ample warning about what was coming, averting an even worse disaster.

On Monday, some 5,200 people were working across the state to restore the situation to normal.

In neighboring Rio Grande do Sul state, the situation was less serious with only about 200 people forced to flee their homes and about 1,000 houses damaged by the storm.

"Here the winds only reached about 50-56 mph," said civil defense Capt. Gustavo Souza.

Although I'm not entirely familiar with the meteorological phenomena of the South Atlantic Ocean, I can say that most atmospheric phenomena tend to occur in cycles; therefore, this feature of Brazilian weather may repeat several times. To whatever extent that it may be a tropical cyclone, the factors that contributed to its development may remain or recur.

From what I can tell, the sea-surface temperatures along the Brazilian coast typically are adequate to support tropical cyclones, albeit marginally. There is considerable net northward transport of near-surface waters at every latitude in the Atlantic Ocean from the Cape of Good Hope to Iceland. The water sinks in several small areas near Iceland and becomes North Atlantic Deep Water. This is the thermohaline circulation.

The sun warms water most intensely in the tropics on average due to greater average incoming solar radiation. Because of the high bulk heat capacity of the oceanic surface layer, the ocean water continues to warm as it moves north of the latitude of greatest solar insolation (which varies considerably by season, and even excluding the polar areas, tends to run somewhat outside the Tropics near the solstices). Somewhat contravening this phenomenon especially in the North Atlantic, warming also takes a considerable period of time, so the maximum sea-surface temperatures occur as late as a few months after the maximum incoming solar radiation.

All of this means that even during the depths of the Northern winter, the axis of maximum sea-surface temperature in the Atlantic does not drift considerably farther south than the Equator. Not coincidentally, the Intertropical Convergence Zone, along which many tropical cyclones develop, tends to follow the axis of maximum sea-surface temperatures. Because of the juxtaposition of the continents, the northward transport as part of the thermohaline circulation, and the typical inadequacy of the Coriolis force within a few degrees of latitude from the Equator, tropical cyclones are extremely rare in the South Atlantic Ocean.

But there is a small area near the Brazilian coast with adequate sea-surface temperatures for tropical cyclones to develop. (There is some question as to the threshhold minimum sea-surface temperature for tropical cyclogenesis during ice ages; however, that's a debate for another time.) It appears that tropical cyclogenesis in this rather small area is inhibited by a combination of:
(1) a general separation from the intertropical convergence zone, which never drifts sufficiently far south for disturbances along it to develop into anything more serious than an occasional tropical wave.
(2) the target area with adequate sea-surface temperatures is small, and the season during which those temperatures are adequate is short, generally January through March. The sea-surface temperatures are adequate but marginal, unlike the Gulf of Mexico during the height of the tropical season.
(3) vertical wind shear. Topography and geography of continents may play some role here, as will the Madden-Julian oscillation. But non-tropical weather systems (cold fronts) oftentimes tend to generate or enhance shear in areas somewhat removed from the Intertropical Convergence Zone. The Hadley ciruculation and associated subsidence can suppress convection necessary for tropical cyclogenesis, but that is not at issue in Porto Alegre.

My inclination is to say that this is too far south, too late in the season to be a hurricane on the grounds of inadequate sea-surface temperatures at Porto Alegre (30°S). It's probably a subtropical cyclone of some sort. But if it approached the city from the north as it probably did, it could be a hurricane moving along the coast.

My inclination is to say that this is too far south, too late in the season to be a hurricane on the grounds of inadequate sea-surface temperatures at Porto Alegre (30°S). It's probably a subtropical cyclone of some sort.

Nope. The definition of "subtropical" is fairly narrow.

It was subtropical for a time (transitioned from a cutoff extratropical low to subtropical) but rather quickly became fully tropical.

It was fully tropical when it hit, and had been fully tropical for several days beforehand.

There's a characteristic appearence on satellite and the storm was blatently tropical in all respects.

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