Hurricane watches and warnings will come out 12 hours earlier beginning this season, a change that might scare a few tourists but will be met by a shrug from storm veterans along the coast.
The more important, but less noticeable, change is the incremental improvement in the National Hurricane Center storm track forecasts. The three-day forecast margin of error is half what it was 20 years ago.
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Last year, the storm track cone — using the current position of the hurricane’s eye to forecast where the eye might be three days later at landfall — would have covered a 125-mile swath of coast. Twenty years ago, the three-day cone would have covered 250 miles of coast. (The forecast cone covers more of the coastline if the hurricane is coming in at an angle.)
The cone is based on a five-year average of forecast accuracy. Because the past few years’ forecasts have been particularly accurate, the width of the cone three days out will shrink by about six miles this year, according to Bill Read, director of the National Hurricane Center. That’s not much, but it’s a continuation of a positive trend.
The watch/warning change is one of several modifications in the National Hurricane Center’s routine this hurricane season, which officially begins June 1. A hurricane watch will be issued 48 hours before hurricane-force winds are possible, and a hurricane warning will be issued 36 hours before hurricane-force winds are expected. Those used to come 36 and 24 hours out.
“With the ever-increasing population along the United States coastline, communities need more time to prepare for tropical cyclones,” according to the hurricane center announcement about the changes.
The hurricane center feels more confident earlier in its forecasts now. More satellites and ocean buoys are providing more accurate information on atmospheric and sea surface conditions than ever before. And each year, that additional information adds to the statistical data fed into computer programs that project hurricane paths.
Local experts think the earlier implementation of watches and warnings should have little impact.
“It won’t change things much in terms of evacuation behavior,” said Susan Cutter, a USC researcher who has done extensive work on hurricane evacuations. “Watches and warnings are only one piece of information that residents look at in deciding to evacuate. And a lot of people living in the coastal areas, particularly in South Carolina, are pretty hurricane savvy.”
Coastal media report the five-day forecast, and many coastal residents know where to go on the Internet to find those five-day forecast cones even before the media has time to report it. They’re tuned in long before watches and warnings are posted.
“Where it might make a difference is in the tourist population,” Cutter said. “They don’t know as much about evacuation.”
If tourists decide to leave two days before a storm hits instead of 36 hours before, that might be a minor blip in the coastal economy. It could make the traffic jam slightly less severe if a full-scale evacuation is necessary 12 hours later.
But most tourists already on the coast rely on the local media or their hotel or rental company for advice, and those advisers pay attention long before watches and warnings are posted, said Brad Dean, president of the Myrtle Beach Area Chamber of Commerce.
A few years ago, tourism officials lobbied against the National Hurricane Center’s publicizing a five-day forecast cone in addition to a three-day cone. They felt the five-day forecast wasn’t accurate enough to put it out there and scare away business.
The slightly smaller cone this year marks needed progress, Dean said.
“The best thing that can help businesses, emergency personnel, everybody, is improved forecasting,” Dean said. “Everyone benefits as they improve the forecasts.”