Waiting For Hurricane X

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It's hard to say precisely when the shift to more frequent hurricanes began. It probably started with the exceptionally intense seasons of 1995 and 1996. The past year, to be sure, was exceptionally quiet, possibly due to the recent El Nino, which tends to suppress Atlantic hurricanes. But now things are hopping again. Just days before Bonnie hit, a tropical storm struck Texas and caused extensive flooding. Even as Bonnie ran out of steam, a new hurricane, Danielle, was barreling across the Atlantic behind her. Meanwhile, by the end of last week, hurricane forecasters had begun watching a new tropical disturbance whirling in the western Caribbean.

No one knows why these cycles occur. According to Bill Gray, a hurricane expert from Colorado State University, one reason may be a phenomenon known as the "Atlantic conveyor." The subject of much recent research, the conveyor is a gigantic oceanic flywheel that transports cold water from the seas off Iceland and Greenland in a majestic, slow current along the bottom of the ocean to Antarctica, where it surfaces several decades later and flows back north, absorbing heat as it passes the equator. The conveyor seems to have kicked into a faster gear lately, bringing warm equatorial water north before it can cool. Hurricanes draw their energy from warm water.

Whether this turns out to be the key factor or just one of many, the trend toward more damaging hurricanes is clear. The reason was made explicit in a study done by Christopher Landsea, a research meteorologist with National Oceanic and Atmospheric Administration's Hurricane Research Division in Miami, and Roger A. Pielke Jr., a social scientist with the National Center for Atmospheric Research in Boulder, Colo. They looked at the most destructive hurricanes in U.S. history and then, says Pielke, posed the question: "If history repeats itself, and it certainly will, what might we expect?" To answer it, the researchers did not simply adjust the original damage totals for inflation. They also included data on the great increase in population, wealth and development that had occurred over the decades in the places where the storms struck.

Looked at in this light, 1992's Hurricane Andrew, officially the costliest hurricane on record with damage, in today's dollars, of $35.5 billion, dropped to second place. The first was a Category 4 hurricane (wind speeds above 130 m.p.h.) that struck southeast Florida in 1926 and skipped into Alabama. (It has no name because the custom of naming storms began only in the early '50s.) If that storm took the same path today, it would cause damage totaling $77.5 billion. Of the 10 costliest hurricanes of the century, nine occurred before 1970. The only recent hurricane to make Pielke's and Landsea's Top-10 list was Andrew.