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Saturday, August 9, 2003 6:38AM EDT
Getting ahead of storm surge
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By BARBARA BARRETT, Staff
Writer
A group of technicians in
life jackets and hard hats huddled on the stern of the R/V Cape Hatteras last
week, readying to plunge 2 1/2 tons of weather instruments deep into the
Atlantic Ocean.
"All right, pull that right there! Pull that right there!" a voice yelled. A
video camera captured the action as a giant red-and-yellow buoy settled into the
ocean with a splash, its bottom strung with instruments that will harvest a rich
crop of data about coming hurricanes.
The technicians, from N.C. State University, know the frustration coastal
residents feel each summer and fall, waiting for hurricanes and wondering
whether they'll have to flee a storm surge.
Now, science aims to reduce the uncertainty.
By the time the first storm approaches this year -- if it comes -- scientists
in the Carolinas plan to use complex computer models to predict the storm surge
better. They hope they can tell emergency officials exactly who needs to be
evacuated and who doesn't.
Things got well under way last week , when technicians lowered three moorings
onto the ocean floor miles offshore near the Sunset Beach pier. The group will
leave port again Monday on the first of two more trips to dump moorings near
Charleston and Hilton Head in South Carolina.
Data will fly back to laboratories by way of satellite.
Len Pietrafesa , a fluid physicist at NCSU, and his colleagues say they can
plug the numbers into a computer, update the information every two hours or so
and predict, almost by city block, where a storm surge is likely to hit.
They can show how quickly the water might rise, how high it might climb and
how soon it might recede.
"I don't know how to say this, but scientists don't often get the opportunity
to help people at the time they need the help, when they actually need it," said
Pietrafesa, who isn't going on the boat trips. "So when you do, it's very
rewarding."
Emergency management officials like the idea.
"Any kind of data I can get that I can translate into heights of water back
in these creeks and tell communities, 'You need to leave,' that would be helpful
to me," said Mike Addertion , director of Carteret County's emergency management
agency.
Over the years, emergency management officials in North Carolina have been
mostly successful in persuading people on barrier islands and in oceanfront
homes to take off when hurricanes come calling. According to the National
Weather Service office in Raleigh, only one death in the state was attributed to
storm surge between 1970 and 1999.
But the surge also creeps miles inland, wreaking havoc in estuaries and the
tangle of streams that feed them. It's the people who live along those waterways
that emergency officials really worry about.
"A lot of people believe, since [they] don't live right on the ocean, that a
hurricane event is a beachfront event," Addertion said. "In fact, the highest
water we find is often back in the creeks somewhere. It's just a tighter space,
and it rises higher."
For now, officials assume the worst and direct everyone to the exit routes.
When Hurricane Floyd plodded up the coast in 1999, the largest evacuation in
U.S. history poured more than 2.6 million people onto clogged highways from
Florida to North Carolina.
The weather service has some surge forecast models, but they could be better,
said Jeff Orrock , the warning coordination meteorologist in Raleigh.
"We're not that good," he said.
Knowing this, scientists at NCSU have teamed with partners at the University
of South Carolina and UNC-Wilmington to improve their storm surge forecasts. The
group secured a two-year, $5 million appropriation from the National Oceanic and
Atmospheric Administration to put out moorings and work on their computer
models.
The instruments will offer accurate information on the wind, waves and
currents, allowing scientists and forecasters to understand the ocean as never
before, said Madilyn Fletcher , director of the Baruch Institute for Marine and
Coastal Sciences at USC .
The group is trying to work as quickly as possible, before any hurricanes
come this way. At least two more boat trips are scheduled in the next few weeks
to drop the instruments.
But sending the moorings overboard is a delicate task. Each strand weighs 2
1/2 tons and is dotted with instruments that cost at least $125,000.
"It's pretty stressful out there," said Billy Sweet , an oceanographer at
NCSU who helped design the moorings.
The moorings include a critical $25,000 piece of equipment called the
acoustic Doppler current profiler, or ADCP.
The ADCP, anchored on the ocean floor, sends sound waves up, bouncing off
plankton and fish, to tell scientists how fast and in which direction the water
is moving, buffeted by wind, tides, pressure and the Gulf Stream. (Sometime this
month , that information is expected to be online for the public at http://www.carocoops.org./
When a storm gets close to shore, the data will come back more frequently.
Pietrafesa's group will start running the animated models, little cartoons on
the computer monitors that show rivers swelling with dark green, yellow and then
red as the water gets deeper and deeper.
"You can see the evolution of the storm, and that is very meaningful,"
Pietrafesa said.
Still, scientists want to be careful about what they tell the weather
service, and they stress that the models have limits. For instance, they don't
predict flooding related to rainfall.
"We have to be extremely careful in how we fold this out, because you're
dealing with people's lives and people's property," Fletcher said.
If this year's program works well, the group hopes next summer to upgrade
other moorings off North Carolina.
"Now the question is, are [the models] as good as we think they are?"
Pietrafesa said. "If they're not, how can we make them as good as they need to
be? If we can do that, we know we can predict the future.
"And that's what forecasting is about."
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