2013 repeat of Irene unlikely--but uncertain too, experts say


By Jim Poole

Two hurricanes may make landfall on the East Coast this year, but when and where are uncertain.
And will one of the hurricanes reach as far inland as Schoharie County, as Irene did two years ago?
That's unlikely but uncertain, too, according to Len Pietrafesa, a lead scientist with a hurricane-prediction team.
A professor emeritus from North Carolina State University, Dr. Pietrafesa works with HUGO, a hurricane study group at Coastal Carolina University in South Carolina.
Like other hurricane predictors, HUGO uses a variety of data to forecast storms. But it also uses historical data from 1950--when the Navy and Air Force began more sophisticated reporting--to look ahead each hurricane season.
"The data sets are really robust in what the outcomes were for every individual event," Dr. Pietrafesa said in a telephone interview.
This year, the HUGO team is predicting one and possibly two hurricanes will hit land on the East Coast during the hurricane season: the last week of August and all of September.
As a storm develops, HUGO is able to "reduce the cone of uncertainty" and give emergency management officials more accurate warnings, Dr. Pietrafesa said.
"We can give a sequence of events and say, 'Evacuate this area first' or 'There will be this much water,' " he said.
Most of those landfalls are in Florida, the Carolinas, Virginia and Maryland.
Those hurricanes that strike farther north are more rare. Since there are less data, predicting those landfalls is more difficult.
Once a hurricane forms, its intensity depends on the warmth of the ocean below it. Ocean current, atmosphere and climatic conditions determine its track.
After a hurricane moves inland, however, tracking becomes more difficult.
"River systems are part of the challenge," Dr. Pietrafesa said. "A lot of this hasn't been appreciated by scientists."
Although hurricanes that strike coastal areas create devastating damage, similar devastation can happen inland, even if such storms are rarer--as Schoharie County is aware.
"Rivers are deep in the middle but can only fill up to the top [of the banks]," Dr. Pietrafesa said.
"Then you have that explosive, lateral flooding."
Overall, HUGO predicts that this hurricane season will be more active than usual for the entire East Coast.
Still, because the numbers of hurricanes that make landfall in the north are relatively few, predicting them is tough, he said.
Predictions should be more accurate once the season is in full swing.
"As climatic conditions change, we can say, 'Given the following conditions, this will happen,' " Dr. Pietrafesa said.
"Once a storm forms, we think we can say with a reasonable degree of certainty where it will end up."