We're overdue for a big wallop

When it comes to hurricanes, statistically speaking, our time is up.

That's what the National Hurricane Center in Miami said in a recent recalculation of "return periods," the average number of years between major hurricanes.

Using historical data, the hurricane center said Charleston should expect a Category 3 or higher hurricane every 15 years.

Hugo slammed into South Carolina 18 years ago.

"We're slightly overdue," said Jon Jelsema, a forecaster with the National Weather Service in Charleston.

The study, titled "The deadliest, costliest, and most intense United States Tropical Cyclones from 1851 to 2006," shows which cities are likely to get walloped the most.

Miami tops the list with a return period of just nine years; Cape Hatteras is second at 11 years.

Return periods diminish markedly south of Charleston before rising again in southern Florida.

Hilton Head, just 100 miles to the south of Charleston, has a return period of 24 years.

Lucky Savannah has a 34-year return period, longer than any city south of Virginia.

"A lot of that has to do with the curvature of the coast," Jelsema said. As a storm spins toward Florida and Georgia, its western winds generate friction with the land, causing the storm to steer north, he said.

Think of a wheel spinning counterclockwise toward a wall: When the wheel finally touches, friction causes the wheel to spin up the wall. The warm waters of the Gulf Stream also help steer storms north.

The report found that Hugo, a Category 4 hurricane, remains one of the costliest storms in U.S. history, when damages are adjusted for inflation.

Hugo ranks sixth at $13.5 billion. Katrina was by far the worst at $85 billion, followed by Andrew at $48 billion, Wilma at $21 billion, Charley at $16 billion and Ivan at $15 billion.

The report cites sociologists who found that people tend to remember the worst effects of a hurricane for seven years.

"It's best to be prepared," Jelsema said. "It's a matter of when we get hit by a major hurricane, not if."