Hurricane forecasting remains a struggle

MIAMI — When a hurricane like Gustav forms, people often have two questions for forecasters: Will it hit me? How strong will it be?

Weather experts have become better at determining where a hurricane will hit, but they acknowledged they have little skill in figuring out its intensity well ahead of time.

With that in mind, government officials try to strike a balance between caution and stirring up unnecessary fear. That's the challenge with Hurricane Gustav, which has many on edge along the U.S. Gulf Coast.

In the past 20 years, forecasters have reduced their errors predicting a storm's path by more than half.

But over the same time, the accuracy of intensity forecasts is virtually unchanged. Those are off by an average of 25 mph, five days in advance, a margin of error that can mean the difference between a low-end Category 1 hurricane and a devastating Category 4. Average error improves to about 12 mph, a day in advance.

Scientists have a limited understanding of how hurricanes form and interact with the atmosphere and the ocean.

National Hurricane Center Director Bill Read knows his forecasts can prompt griping from people who evacuate only to see the storm hit miles away or fizzle out. But emergency managers often have no choice.

Read said the government's goal is to cut tracking errors in half again in the next decade. Improvements in intensity predictions are harder to promise.

"I would be ecstatic if we could, say, correctly forecast half of the time, 24 hours in advance, a rapid change in intensity," he said.