Authorities are still tabulating an official death toll from Katrina. Early fears that as many as 10,000 had been killed seem to be ebbing as rescue workers are finding fewer bodies.
Still, the number killed in Louisiana, Mississippi, Alabama and Florida has topped 500far more than have been killed by a hurricane in the U.S. in decades.
The cost of the damage inflicted on the Gulf Coast by Hurricane Katrina is expected to dwarf that of the 1992 season, when Hurricane Andrew claimed the highest damage total until this year.
Andrew's eye went ashore just south of Miami in August 1992. The storm's winds, which exceeded 155 miles an hour (249 kilometers an hour), cut a swath of devastation across densely populated southern Dade County.
Hurricane Andrew caused damage totaling about 35 billion dollars (U.S.) when adjusted for inflation.
The cost of Hurricane Katrina is only beginning to be calculated, but it's expected to be staggering. Early estimates predict that the cost will easily exceed 200 billion dollars and could approach 300 billion dollars.
The devastating and deadly 2005 hurricane season continues a trend of stormier summers that began in 1995. Gray and other research meteorologists say that active hurricane seasons are cyclical. The cycles of active seasons can last several decades.
The most active hurricane season on record is 1933. That year 21 tropical storms formed. Of those storms, nine developed into hurricanes, and five of them became major hurricanes with winds of at least 111 miles an hour (249 kilometers an hour).
The second-most active season on record was 1995, when 19 tropical storms formed.
Gray and his colleagues say the alternating cycles of active and less active hurricane seasons are caused by fluctuations in the salt content of ocean water. When the water has a higher level of saltas the Atlantic does nowthe water is warmer. That, in turn, spawns more tropical storms.
Some meteorologists think that global warming is contributing to the increase in hurricanes and making the storms more intense.
But Gray disagrees with this theory. When the total number of tropical storms and hurricanes around the world are added up, he says, "there has actually been a slight decrease since 1995."
Willie Drye is the author of Storm of the Century: The Labor Day Hurricane of 1935, published by National Geographic Books.
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