May/June 2006Climatologist Helps Weathermen: Emergency Planners Make the Callby Marc Rapport

The state climatologist doesn't make the forecasts; she helps make the forecasts better.

As the state climatologist at the S.C. Department of Natural Resources, Hope Mizzell and her colleagues study reams of data from storms past and present to help forecasters, planners and responders determine the likely impact of tropical systems as they spread water and wind over land.

Climatologists draw on data old and new to help make those calls, providing history and context. That includes the two dozen or so forecast software models deployed on a moment-to-moment basis using satellite and radar imagery, as well as historical records. For instance, the strongest storm ever to hit South Carolina may have been an estimated Category 4 that struck around Charleston in 1752.

National Hurricane Center Average Official Track Forecast Errors for the Atlantic Basin

Forecast Period Error (statute miles)
12 hours 52
24 hours 92
36 hours 132
48 hours 167
72 hours 247

Depending on the strength and track of the hurricanes, SC Emergency Management Division must start evacuations 24 to 48 hours before tropical storm winds begin to impact an area. This table shows the average National Hurricane Track errors for 24 to 72 hour forecast periods. If an Emergency Manager is faced with making an evacuation decision 48 hours in advance, the average track error is 167 miles, basically the distance of the entire South Carolina coast. Unfortunately while the track errors are getting smaller every year the coastal population continues to grow, resulting in longer evacuation times.

How do we know that? Cary Mock, a hurricane geographer at the University of South Carolina, says that determination was based on published reports and known water lines on structures, some that still exist 250 years later. "There were accounts of ships pushed thirty miles inland," he says.

What would such a storm do now? Forecasters and planners have one tool, the aptly named SLOSH (sea-lake overland surge hike) maps that show that such a storm could produce fifteen feet or more of storm surge, overrunning the Battery and causing flooding miles up the Ashley and Cooper rivers.

In Beaufort and Jasper counties, the water could push even farther, reaching as far inland as Interstate 95. Meanwhile, Myrtle Beach is on a bit of a ridge, potentially keeping the surge even from a Category 5 inside US Highway 17.

Local knowledge like this is what the state climatologist employs to help forecasters and planners better warn the public what to expect as storms move in.

"We provide the science to the state Emergency Management Division, to help them better know what to expect," says Freddy Vang, deputy director of the Land, Water and Conservation Division of the DNR.

Mizzell adds, "We use our knowledge of climate and history to help say how much rainfall a storm might bring, and where, and what kind of tornado outbreak could come along with it.

"We also help the EMD make sure its tracking software is as up-to-date as it can be. We also are testing software that gives us access to private weather stations, at schools and other places, to decide if their information would be useful to us and to EMD."

Mizzell says she's seen two major changes in recent years. One, of course, is technology, perhaps most visible in the improvement in tracking storms and predicting landfall. The other is a greater appreciation for inland impacts.

"Hugo had a lot to do with that. And people are a lot more aware now that storms coming off the Gulf of Mexico can be just as bad for us as those coming off the Atlantic. Remember, Frances caused forty-six tornadoes here in 2004, and Jerry dropped as much as twenty inches of rain in the Upstate in 1995," the state climatologist says.

Getting hurricane information out to the public, of course, is a key function of the EMD. The division's Emergency Operations Center at the old National Guard armory in Pine Ridge includes space and electronic hookups for the media, notes Jon Boettcher, EMD's hurricane program manager, and the division also puts out annual hurricane season readiness guides in English and Spanish.

Getting the word out also can involve door-to-door announcements of evacuations when they're called, something that DNR does on the barrier islands.

But is it enough? "We've got the National Hurricane Center, the National Weather Service, the state climate office, Emergency Management Division, and our own people, and I'm still not sure we're communicating strongly enough the potential impact on property and on lives," Mizzell says.

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