Waiting For Hurricane X

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Another potentially lethal factor: hurricanes can suddenly change in intensity. For Jerry Jarrell, director of the federal Tropical Prediction Center (which includes the National Hurricane Center), the most frightening near miss was not Andrew but Hurricane Opal, which hit the Gulf Coast in October 1995. Opal had been a weak storm, but just before it struck, it underwent what forecasters call "rapid deepening," leaping from Category 2 to nearly Category 5, with winds at 150 m.p.h. It also started moving faster. Such rapid change is the thing emergency managers most fear. Says Tom Millwee, coordinator of the Texas Division of Emergency Management: "You go to bed thinking you've got a Cat 1 moving at 10 m.p.h. You wake up, it's a Cat 5 moving at 20 m.p.h."

The sudden change threw evacuation plans into chaos. Most people waited until morning to evacuate, and did so in a vast crush of cars. Road construction further slowed progress. By morning the scene along Interstate 10 outside Pensacola was like something from a grade-B disaster film. Jarrell estimates 10,000 people were stranded on the highways, listening to ever more urgent broadcasts on their radios. Some drivers abandoned their cars and fled for high ground.

Then, just before landfall, Opal had another change of heart. She fizzled. By the time the storm crossed the coast, its winds diminished by at least a third. Until then, however, it fit Jarrell's vision of what the Big One will be like: traffic jams and cars blown wholesale into storm-surge waters. "I'm afraid you're going to drown hundreds if not thousands of people," says Jarrell. "And it's going to happen some time."

One of the darkest scenarios, however, envisions a powerful storm of Category 4 or higher making a direct hit on a major city like New Orleans or Miami. Surprisingly, hurricane researchers now consider one of the most vulnerable targets to be downtown New York City. They made the discovery by accident, in the course of a routine storm-evacuation study begun in 1990 by the Army Corps of Engineers, the kind of study done for every large community on the nation's hurricane-prone coasts. "We were all shocked," says Allan McDuffie, the Corps' study manager.

They discovered that the city has some unique and potentially lethal features. First, they realized that its major bridges, like the Verrazano Narrows and the George Washington, were so high they would experience the advance winds of an approaching hurricane several hours before winds of the same velocity were felt at ground level. These critical escape routes would have to be closed well before ground-level highways.

Even more surprising, however, were the results of computer models done with a federal computer program called SLOSH, which stands for Sea, Lake and Overland Surge from Hurricanes. The program, the backbone of all evacuation studies, takes into account storm tracks, local landmarks and coastal geography to calculate the effects of a hurricane storm surge, the dome of water pushed ashore by strong winds. Such surges can be the deadliest aspect of a hurricane. An immense surge overflowed the city of Galveston, Texas, in 1900 and killed more than 8,000 people, and possibly as many as 12,000. A surge raised on Florida's Lake Okeechobee in 1928 killed 1,836.