- The Washington Times - Tuesday, September 16, 2003

Forecasters are predicting confidently that Hurricane Isabel will strike the North Carolina coast, but they won’t be able to give an accurate prediction about the strength of the slow-moving storm until a few hours before it makes landfall.

While forecasters have developed a reliable method to determine where hurricanes will strike days before their arrival, predicting a hurricane’s wallop more than 12 hours before landfall still is a tough job.

“Everyone knows that’s a problem that needs to be solved,” said John Kaplan, research meteorologist at the National Oceanic and Atmospheric Administration’s Hurricane Research Division in Miami.

Difficulty determining hurricane strength has serious public safety implications. More accurate predictions of a storm’s wind speed on land could help local, state and federal safety officials make better decisions about preparations and evacuations.

Maryland Gov. Robert L. Ehrlich Jr. declared a state of emergency last night, calling the National Guard to active duty status so troops will be ready when Isabel strikes. “We’re not expecting the worst, but that could change,” the Republican governor said.

In North Carolina yesterday, Gov. Michael F. Easley, a Democrat, declared a state of emergency as the Outer Banks and other beach areas were evacuated. Residents from South Carolina to New Jersey boarded up homes and businesses. In the Washington area, officials buttressed riverbanks and the region’s integral transit system with sandbags.

Isabel’s winds, which reached 160 mph during the weekend, were reduced to about 105 mph yesterday.

What is not clear is whether the storm will weaken further, but forecasters say Isabel could strengthen over warmer waters as it approaches the Outer Banks.

Mr. Kaplan developed the method used to forecast the wind speed of hurricanes with research meteorologist Mark DeMaria. The Hurricane Research Center has used the method since 1995.

Even while it is viewed as the best way to forecast a hurricane’s intensity, its effectiveness remains in question.

“If there’s a weak link, it’s the intensity forecasting. There is a lot of research being done now on that. We understand the dynamics of a storm’s movement, but we don’t understand the factors that control the intensity,” said Dan Kottlowski, senior meteorologist at Accuweather.com, which supplies weather information to television and radio stations.

Last year, wind speed forecasts two days before a storm’s landfall were off by an average of 17 mph, according to statistics compiled by the Hurricane Research Division. That is nearly the difference between a Category 2 hurricane, which has top winds of 110 mph, and a Category 4 storm, which has a minimum wind speed of 131 mph.

Forecasts of wind speed made 24 hours before landfall were more accurate, but still off by an average of 10 mph.

“Obviously, we’d like to do better, but that’s as good as we can do right now,” Mr. Kaplan said.

The method — called the statistical hurricane intensity prediction scheme — compares hurricane data with statistics compiled about prior storms.

“It does a pretty good job, but with intensity modeling, we’re maybe 20 years behind our ability to do track forecasting [to predict the path a storm will take],” Mr. DeMaria said.

Pressure to make accurate predictions about storm strength springs from a desire to improve emergency preparedness.

“If you’re expecting a Category 1 storm and you get a Category 5 storm, you can have some problems with evacuation,” Mr. DeMaria said.

Hurricane forecasters also are worried about overestimating a hurricane’s danger, said Frank Marks, director of the Hurricane Research Division.

Hurricane Research Center officials say it costs an average of $45 per person to prepare for a hurricane. That includes everything from the cost of bottled water and generators to wood to board up windows.

If forecasters overestimate a storm’s intensity, evacuation may be more widespread than needed, said Ed Rappaport, deputy director of the Hurricane Research Center.

“At $45 a person, that can amount to millions of dollars in preparedness costs,” he said.

Forecasters account for their margin of error by urging state and local officials to prepare for storm intensities one category higher than they expect. If a Category 2 hurricane is predicted to make landfall, forecasters suggest treating the storm like a Category 3.

“That means we can end up preparing more than is sometimes necessary,” Mr. Rappaport said. “In the future, we may not have to consider the possibility of a storm coming ashore that is one category stronger than we forecast.”

Forecasters are struggling to understand all the factors that affect a storm’s strength, said Kerry Emanuel, professor of atmospheric science at the Massachusetts Institute of Technology.

“We’re fairly confident that we can do a much better job than we’re doing now,” he said, but no significant changes in intensity forecasting are expected until at least 2006.

“Everybody wants the forecasts to be better,” Mr. Kaplan said. “It’s just a really hard problem to solve.”

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