Force Of Nature

As Hurricane Ivan continued its savage sweep through the Caribbean, devastating the little island of Grenada and battering Jamaica, Stanley Goldenberg, a research meteorologist with the National Oceanic and Atmospheric Administration in Miami, got ready to fly out over the frenzied ocean. As a scientist, Goldenberg was thrilled by Ivan's wild beauty. As a longtime resident of Dade County, he was worried about the welfare of his wife and kids.

Like other Floridians, Goldenberg found the onslaught of wind and rain over these past few weeks somewhat surreal. No sooner had residents of the Sunshine State draped tarps over roofs damaged by Charley than Frances came along. And no sooner had they started to clean up after Frances than Ivan loomed. And yet, reflects Goldenberg, the real wonder is that Florida has been spared for so long. "I'm in shock over the damage and the deaths, but I am not surprised," he says.

Starting a decade ago, scientists began warning coastal-zone residents that big hurricanes were once again headed their way. As if to underscore the point, 1995 produced 19 named Atlantic Ocean storms, the second busiest season on record (after 1933, which had 21). Most years since 1995 have followed a similar trajectory. Colorado State University hurricane expert William Gray is now projecting a total of 16 named storms for 2004, including five major hurricanes.

By contrast, the period between 1970 and 1994 averaged less than two major hurricanes per year, which raises the central question of this hurricane season: Why is the Atlantic producing so many big storms these days? The reason, believes Goldenberg, lies in a broad 1°F-to-1.5°F rise in sea-surface temperatures that occurred in the mid-1990s. That slight but significant increase is thought to be due to a cyclical shift in ocean-circulation patterns. When the Atlantic last warmed, between 1926 and 1970, a parade of monster storms menaced the Caribbean and the coastal U.S. Then, between 1970 and 1994, sea-surface temperatures dropped, and, save for Andrew in 1992, a long and pleasant hiatus in hurricane activity ensued.

Scientists are trying to figure out how fluctuations in sea-surface temperatures affect storm formation. Part of the influence is direct; warm water is like high-test fuel to hurricanes. But it's more complicated than that, experts believe. The change in sea-surface temperatures parallels atmospheric changes that have been linked to everything from the strength of ocean trade winds to the amount of rain that falls across the U.S.

Not all hurricanes slam into land, of course. Whether that happens is determined by so-called steering currents--wind patterns set up by high-pressure ridges and low-pressure troughs. Steering currents can push hurricanes away from a particular area or directly toward it. And what worried forecasters as Ivan bore down was that these currents seemed almost malignantly aligned to ensure that both the Caribbean and Florida remained in the storm's deadly cross hairs.