measure of a storm’s potent punch – the storm surge
Coastal Review Online
Hurricane Irene moved up the East Coast just about a year ago, Joseph
DiRenzo, the chief of operations analysis for the Coast Guard Atlantic
Area, placed a phone call from his office in Portsmouth, Va., to Rick
Luettich, director of the University of North Carolina’s Institute
of Marine Sciences in Morehead City.
was worried about the Portsmouth base, which is the Coast Guard’s
command center for the Atlantic. It sits on very low ground that is
prone to flooding. Though Irene wasn’t forecast to become a major
hurricane, the famous five-category scale used to distinguish storms is
based on sustained winds. It says nothing about a storm’s
most-dangerous feature—its surge of floodwaters. DiRenzo wanted to know
what kind of storm surge to expect in Portsmouth.
phone call turned out to be the key decision in a string of moves that
helped keep the Coast Guard fully operational as Irene, a big storm but
only a Category 1 hurricane when it made landfall in North Carolina,
surprised many, wreaking havoc along the Eastern Seaboard all the way
into New England.
had served on an advisory board for the U.S. Department of Homeland
Security’s Coastal Hazards Centers of Excellence, a consortium of
hundreds of universities that work on ground-breaking technologies. UNC
is part of the network. DiRenzo knew Luettich, having bumped into him
many times over the years at meetings. More importantly, he knew of
Luettich’s involvement in developing and pioneering a system of
computer models that’s remarkably accurate in turning raw data –
hurricane wind speeds and paths – into predictions of the amount of
storm surge that might be expected in specific locations.
DiRenzo’s request, Luettich ran the Advanced Circulation Models, or
ADCIRC, on powerful computers in Chapel Hill. It was quickly evident
there would be problems in Portsmouth.
fact, Luettich said recently, the models indicated that the base would
be inundated. Forewarned, base commanders in Portsmouth loaded two
C-130 aircraft, one carrying command staff, and flew them to St. Louis
to ride out the storm and control Coast Guard operations from Missouri,
900 miles away. Not too long after that, the base was indeed flooded by
storm surge and lost power.
was not, however, the first time the U.S. government had made use of
ADCIRC. Luettich said the Army Corps of Engineers has made extensive
use of the program’s modeling capabilities to guide construction of new
levees and other flood control measures in the New Orleans area in the
wake of the devastation caused by Hurricane Katrina in late August
2005. Billions of dollars worth of construction have been based on
ADCIRC models’ predictions of how future storms will likely impact the
been a long time coming.
since I’ve been at UNC, about 20 years, I’ve been working on programs
to predict how the coastal ocean moves,” Luettich said. “I’ve been
interested not only in how and where the water moves, but also the
movement of fish larvae and contaminants in the water. As this program
has evolved, it has improved to the point where it is useful to a
variety of agencies.
not the first of its kind, but it does represent a major leap forward,”
he said. “Previous programs were smaller and limited.”
difference, Luettich said, is the extensive underlying database
developed for and used by ADCIRC.
basic software – the algorithms – has stayed basically the same, but
our underlying database is now very site-specific,” he said. “In the
greater New Orleans area, for example, we worked down there for four or
researchers – Luettich’s prime collaborators are at Notre Dame – have
used topographic and other crucial data from a wide array of sources,
from federal agencies – NOAA and Army Corps of Engineers, for instance
-- down to the county level.
is the case for most “products,” improvement has been driven by demand.
As more people and more agencies have used ADCIRC data, they’ve wanted
more out of it. To provide that, Luettich and his team, including
graduate students, have had to continually refine and improve the
program, which can be, and has been, used in crucial decisions about
whether to move large vessels to safer places as storms approach.
are big decisions,” Luettich said. “It costs a lot of money to move
ships, hundreds of thousands of dollars. You can just say, ‘Move
everything and play it safe,’ but that’s expensive.”
program helps those in charge make those decisions with more
confidence, based on what should be more accurate and location-specific
decisions than in the past, he said.
Luettich said, is now used by the Federal Emergency Management Agency
and consultants from New England south and west to Texas. It’s becoming
program does not obviate the need for data and predictions from the
National Hurricane Center and NOAA’s National Weather Service, Luettich
emphasized. In fact, the program uses that data.
grab the advisories the National Hurricane Center generates for storms
every six hours – wind speed, wind fields, predicted paths, wave
heights, things like that – and use them to drive ADCIRC,” he said. “We
did that for each one they sent out for Irene. Our goal has not been to
supplant what the others do. What we do is ‘value-added.’”
and his team are in the process of spreading the word about the
capabilities of ADCIRC to emergency managers in coastal North Carolina.
He stressed that ADCIRC requires vast computing power, almost that of a
“super-computer,” so it’s not something local emergency managers can do
on their own. During Irene, he said, the institute in Morehead City
lost power, but he was able to look at results of the program in Chapel
Hill by using his battery-powered IPad.
Luettich said, UNC will, on request, run the program for specific areas
and place the results on the program’s web site.
While there, casually interested viewers can select storms – such as
Earl in 2010, Irene in 2011 or Beryl in 2012 – and run animations to
view surge heights at various times.
said the information can be very valuable on a local level, where
managers must try to quickly make sense of very complicated situations
and scenarios. For example, storms’ impacts are very tricky to predict
on the back side of barrier islands in North Carolina’s Pamlico Sound,
which is virtually an inland sea. Hurricanes can literally blow water
away from those shores one minute, to the point where the sound is
“dry” a half-mile or mile offshore, then quickly flood those same
shores when the wind shifts as a hurricane moves past.
Luettich plans to continue to improve the program.
we want to move toward is being able to develop an ‘ensemble’ of storm
scenarios, where we can take a storm forecast, and, say, move it a
little to the left or a little to the right, then maybe run it 20
percent stronger than predicted,” he said. “Storms are very
unpredictable, as all of us here on the coast know. Predictions have
improved greatly, but the storms can wobble, they can strengthen and
we want to be able to do is take the predictions and do variations. If
we can do that, and then present a half dozen or maybe 10 variations,
then we’ll be able to look at a forecast and then just click through
the plausible alternatives. We think that will be very useful.”
story is provided courtesy of Coastal Review Online, the coastal news
and features service of the N.C. Coastal Federation. You can read other
stories about the N.C. coast at www.nccoast.org.)