Nine Hurricanes Predicted for Atlantic Basin This Season

FORT COLLINS, Colorado, April 4, 2007 (ENS) - A very active hurricane season is in store for the U.S. Atlantic Basin starting June 1, but not as active as the 2005 season, according to a team of hurricane forecasters at Colorado State University.

Meteorologists William Gray and Phil Klotzbach anticipate 17 named storms in the Atlantic basin between June 1 and November 30, of which nine will become hurricanes.

Of those nine, the team predicts that five will develop into intense or major hurricanes - rated category 3, 4 or 5 on the Saffir/Simpson scale - with sustained winds of 111 miles per hour or greater.

"We are calling for a very active hurricane season this year, but not as active as the 2004 and 2005 seasons," said Klotzbach. "Based on our latest forecast, the probability of a major hurricane making landfall along the U.S. coastline is 74 percent compared with the last-century average of 52 percent."

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Colorado State University hurricane forecasters William Gray, left, and Phil Klotzbach work with the Tropical Meteorology Project. (Photo courtesy CSU)
The team's forecasts are based on the premise that global oceanic and atmospheric conditions - such as El Nino, sea surface temperatures and sea level pressures - that preceded active or inactive hurricane seasons in the past provide meaningful information about similar trends in future seasons.

For 2007, the forecasters expect continued warm tropical and north Atlantic sea surface temperatures, prevalent in most years since 1995, as well as neutral or weak La Nina conditions - a recipe for greatly enhanced Atlantic basin hurricane activity.

These factors are similar to conditions that occurred during the 1952, 1964, 1966, 1995 and 2003 seasons. The average of these five seasons had well above-average activity, and Klotzbach and Gray predict the 2007 season will have activity in line with the average of these five years.

No hurricanes made landfall along the U.S. coastline last year. The 2006 season developed a total of 10 named storms, five hurricanes and two major hurricanes.

The 2005 season, considered unusual by the Colorado State forecast team, there were 27 named storms, 15 hurricanes and seven intense hurricanes.

Long-term averages are 9.6 named storms, 5.9 hurricanes and 2.3 intense hurricanes per year.

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A Category 5 storm, Wilma became the 12th hurricane of the 2005 Atlantic hurricane season in October, making the 2005 season became the most active on record. (Photo courtesy NOAA)
The Colorado State team has cautioned against reading too much into the hurricane seasons of 2004 and 2005 when Florida and the Gulf Coast were ravaged by four landfalling hurricanes each year. Hurricanes Charley, Frances, Ivan and Jeanne caused devastating damage in 2004, followed by Dennis, Katrina, Rita and Wilma in 2005.

"The activity of these two years was unusual, but within the natural bounds of hurricane variation," said Gray, who began forecasting hurricane seasons at Colorado State 24 years ago. "Following the two very active seasons of 2004 and 2005, 2006 experienced slightly below-average activity with no landfalling hurricanes."

"We've had an upturn of major storms since 1995," Gray said. "We think this upturn of major storms will continue for another 15 or 20 years."

Gray does not attribute changes in recent and projected Atlantic hurricane activity to human-induced global warming.

"Although global surface temperatures have increased over the last century and over the last 30 years, there is no reliable data available to indicate increased hurricane frequency or intensity in any of the globe's seven tropical cyclone basins, except for the Atlantic over the past 12 years," Gray said.

"Meteorologists who study tropical cyclones have no valid physical theory as to why hurricane frequency or intensity would necessarily be altered significantly by small amounts of global mean temperature change," he said.

Gray and Klotzbach predict tropical cyclone activity in 2007 will be 185 percent of the average season. By comparison, 2005 witnessed tropical cyclone activity that was about 275 percent of the average season.

"In December and January, we had a weak to moderate El Nino event in the tropical Pacific Ocean. When you have El Nino conditions during the hurricane season, it increases vertical wind shear across the tropical Atlantic and typically results in a weaker tropical cyclone season," Klotzbach said.

"However, we've seen El Nino conditions dissipate quite rapidly late this winter, so we do not think that's going to be an inhibiting factor this year," said Klotzbach. "Also, we have warm Atlantic sea surface temperatures this year which we've seen just about every year since 1995."

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U.S. Air Force hurricane hunters fly into the eye of an Atlantic hurricane. (Photo courtesy U.S. Air Force)
Gray and Klotzbach said there is a 74 percent chance that at least one major hurricane will make landfall on the U.S. coastline in 2007. The long-term average probability is 52 percent.

There is a 50 percent chance that a major hurricane will make landfall on the U.S. East Coast, including the Florida Peninsula, they said. The long-term average is 31 percent.

They predict a 49 percent chance that a major hurricane will make landfall on the Gulf Coast from the Florida Panhandle west to Brownsville, while the long-term average is 30 percent.

The team also predicted above-average major hurricane landfall risk in the Caribbean.

"We were quite fortunate last year in that we had no hurricane landfalls," Klotzbach said. "The 2006 season was only the 12th year since 1945 that the United States witnessed no hurricane landfalls."

Probabilities of tropical storm-force, hurricane-force and intense hurricane-force winds occurring at specific locations along the U.S. East and Gulf Coasts within a variety of time periods are listed on the forecast team's Landfall Probability website.

The site provides U.S. landfall probabilities for 11 regions, 55 sub-regions and 205 individual counties along the U.S. coastline from Brownsville, Texas, to Eastport, Maine.

Online at: http://www.e-transit.org/hurricane, the site is the first publicly accessible Internet tool that adjusts landfall probabilities for regions, sub-regions and counties based on the current climate and its projected effects on the upcoming hurricane season.

Klotzbach and Gray update the site regularly with assistance from the GeoGraphics Laboratory at Bridgewater State College in Massachusetts.