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ORLANDO, Fla., April 2 (Reuters) - The noted Colorado State University forecast team expects an above-average Atlantic hurricane season and may raise its prediction of 13 tropical storms and seven hurricanes when it updates its outlook next week, the team's founder, Bill Gray, said on Wednesday.
La Nina cool-water conditions in the Pacific and higher sea surface temperatures in the eastern Atlantic are contributing to enhanced conditions for hurricane activity, Gray told Reuters at the U.S. National Hurricane Conference.
"We're expecting an above-average season," Gray said. "The big question we have is, are we going to raise the numbers from our December forecast? We might."
"We're not going to lower the numbers," he said.
The average six-month Atlantic hurricane season produces about 10 tropical storms and six hurricanes -- a standard that was blown out of the water in record-busting 2005, when 28 storms formed, including Hurricane Katrina, which swamped New Orleans.
The 2007 Atlantic hurricane season brought 14 tropical storms, of which six strengthened into hurricanes.
The Colorado State team issues forecasts several times a year. In December, it said it expected the 2008 season starting June 1 to produce 13 tropical storms, of which seven would become hurricanes and three would be major hurricanes with winds of at least 111 mph (178 kph).
Colorado State's forecasts have been well off the mark the past three years. Its next update on expectations for 2008 will be issued on April 9 at a conference in the Bahamas.
Gray pioneered long-range hurricane forecasting, issuing his first seasonal prediction in 1984.
Others followed, including the U.S. National Oceanic and Atmospheric Administration, and private risk assessors.
The fierce storms have captured increasing attention from oil markets, insurance firms and commodities traders because of their impact on U.S. Gulf of Mexico crude production and the devastating damage they can cause to buildings and crops.
Hurricane experts believe the Atlantic is in an era of naturally heightened hurricane activity that began around 1995 and could last up to 40 years. Some -- not including Gray -- say global warming may also be causing more powerful hurricanes.
Gray said he expected a weak to neutral La Nina condition -- a cooling of waters in the eastern Pacific that can enhance conditions for hurricane activity in the Atlantic. The water will be "on the cold side," he said.
La Nina's opposite, El Nino, a warm-water phenomenon that acts to inhibit Atlantic hurricane formation, is not expected to appear during the 2008 season, he said.
"Also, the sea surface temperatures in the eastern Atlantic particularly off Iberia and off northwest Africa, they are very warm, much like they were at this time in 1995 and 2005 when we had very active seasons," he said.
Hurricanes gain strength from warm ocean water.
Temperatures in those areas, which are where many storms form, have climbed from 0.3 to 0.5 degrees Celsius (0.5 to 0.9 degrees F) in the past few months, Gray said. (Reporting by Jim Loney; Editing by Michael Christie and Peter Cooney)
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