"If this outlook holds true, this season could be one of the more active on record," NOAA administrator Jane Lubchenco said in a statement. "The greater likelihood of storms brings an increased risk of a landfall. In short, we urge everyone to be prepared."
A hurricane might help break up the oil spill staining the Gulf of Mexico, but the oil won't affect significantly how tropical storms develop, forecasters said. They don't know what kind of environmental hazards to expect, though there are fears that winds and waves could push the oil deeper into estuaries and wetlands.
Government scientists said Thursday that anywhere from 500,000 gallons to a million gallons a day has been leaking from the site where an oil rig exploded April 20, killing 11 people. BP PLC, which leased the rig and is responsible for the cleanup, and the Coast Guard previously had estimated the flow was about 210,000 gallons per day.
The expanding slick already has coated wildlife and marshes in Louisiana, but Lubchenco said the spill is still small relative to hurricanes -- which sometimes can span the entire Gulf.
Although some oil could be pushed inland by a storm as it makes landfall, it could be difficult to determine whether it leaked from flooded cars or factories, Federal Emergency Management Agency chief Craig Fugate said.
The 2010 government forecast is based on the weakening of El Nino. The Pacific Ocean phenomenon created strong wind shear that helped suppress storm development in the Atlantic last season. Record warm water temperatures also will feed storms crossing the Atlantic this year.
Three hurricanes developed out of nine tropical storms in 2009. None of the hurricanes came ashore in the United States. Hurricane Ida hit Nicaragua as a Category 1 storm in November.
Florida Gov. Charlie Crist urged coastal residents to remember the destruction left in the wake of hurricanes in 2004 and 2005.
"Don't take anything for granted," Crist said at the annual Florida Governor's Hurricane Conference in Fort Lauderdale. "We don't need to suffer from hurricane amnesia."
National Hurricane Center Director Bill Read said Wednesday that his biggest concern for the season is a storm striking Haiti, where hundreds of thousands of people have been living in makeshift camps since the Jan. 12 earthquake. Heavy rains can trigger serious flooding and mudslides in the mountainous Caribbean country, but no evacuation plans exist for displaced communities.
Tropical storms are named when their sustained winds reach 39 mph. The first named storm of the 2010 season will be Alex.
In April, Colorado State University researchers predicted 15 named storms would form this season, with four developing into major hurricanes.
The Atlantic hurricane season begins Tuesday and runs through Nov. 30.