Changing ocean conditions greatly raise the threat level from a relatively benign 2009
The Tropical Meteorology Project at Colorado State University is predicting a volatile 2010 hurricane season - much busier than last year, when Claudette was the only tropical storm to make landfall along the U.S. coast.
The new forecast, published April 7, calls for 15 named storms, eight of them hurricanes. Last year, there were nine named storms, of which three were hurricanes. The new numbers represent an upward revision of the project team's original forecast for 2010.
In December, the team - William Gray, professor emeritus of atmospheric science, and research scientist Philip Klotzbach - had estimated there would be between 11 and 16 named storms, six to eight of them hurricanes. They based that on colder-than-normal Atlantic waters and the possibility of an El Niño effect. Since then, however, ocean conditions have reversed.
Gray says tropical storms will have a clearer window for landfall because of the breakup of El Niño and warmer temperatures in the Atlantic. El Niño is the warming of surface temperatures in the Pacific that hinders the formation of tropical storms.
During an El Niño, westerly winds develop in the upper levels of the atmosphere and easterly winds at lower levels, creating shear - crisscrossing winds. Shear prevents hurricanes from organizing and intensifying into storms with rotating air circulation reaching high into the atmosphere.
"We only had three hurricanes last year, and none of them hit the U.S.," says Gray. "This year we are predicting for the entire U.S. coastline a
69 percent chance a Category 3, 4 or 5 hurricane will hit."
He cautions, however, that it is impossible to precisely predict hurricane activity in early April. He says he and Klotzbach will continue monitoring El Niño and present an updated report June 2.
The boating community, meanwhile, isn't taking any chances. "This is something we do worry about," says Bob Adriance, assistant vice president and technical director for BoatU.S. "Some of the worst hurricanes we've had, such as Hugo  and Andrew , have taken place during less active years than normal."
Adriance says BoatU.S. sent out a press release intended to alert its members to the April 7 report. "Gray is pretty good at predicting these trends," he says.
Adriance says he is not surprised to hear that El Niño is dissipating. "The El Niño effect usually never lasts more than a season, and we've had it in place for the last two years," he says. "But that is paving a way for more hurricane landfall, and none of that is good news."
This article originally appeared in the June 2010 issue.