The federal government predicted today an active hurricane season for 2007 -- with 13 to 17 named storms, of which as many as 10 could become full hurricanes.
Three to five of those could become "major" hurricanes -- category 3 or higher -- with winds of more than 110 miles an hour.
"Years like this have historically had two to four storms making landfall," said Gerry Bell, lead hurricane forecaster at the Climate Prediction Center of the National Oceanographic and Atmospheric Administration, or NOAA.
Government officials urged people to take the warning seriously, noting that 53 percent of the U.S. population now lives within 50 miles of a coastline. And even if the numbers are off, the consequences of a storm making landfall, they said, are no less severe.
"It just takes one hurricane to make it a bad year for everyone here," said Conrad Lautenbacher, head of NOAA.
While generally expressing confidence in the predictions, experts said predicting hurricanes can be an inexact science.
The 2005 Atlantic hurricane season, for example, generated 15 hurricanes. A record four major hurricanes hit the United States, including Katrina, which devastated New Orleans, killed 1,300 people and caused $80 billion in damage.
Forecasters had expected an active 2006 season as well, but only 10 storms formed, five of which became hurricanes. Hurricane experts said El Nino -- the periodic warming of the Pacific Ocean that tends to reduce the number of Atlantic hurricanes -- was largely to blame.
The year-to-year swings, experts said, show how difficult it can be to predict hurricane activity.
Hurricane scientists use a variety of tools to predict how a season will shape up, including computer models, historical trends and general global conditions like sea surface temperature. With all their data and knowledge, however, experts said it all comes down to hurricane forecasters making an educated "best guess."
"They're not going to pin the number accurately, year in and year out," said Florida State University scientist James Elsner. "Most years, they are going to be off by several storms or several hurricanes."
Elsner is a professor of geography at Florida State University in Tallahassee and also runs a company that provides weather risk consulting to insurance and government clients.
Insurance companies use the forecasts to evaluate risks to property along the coasts, although NOAA officials said today they don't know if any hurricanes will hit the United States this season.
"It's currently not possible to confidently predict the exact number or intensity of land-falling hurricanes or whether a given locality will be impacted this season," said NOAA's Bell at Tuesday's press conference.
Elsner believes the hurricane forecasts made by Bell and colleagues are generally reliable. And even though no hurricanes hit the United States last year, Elsner says it was an average season nonetheless.
"If you ask people in Bermuda, it was an active year," he said. "They got threatened twice and hit once."
Elsner believes that overall, hurricane forecasters do a pretty good job and are usually on target.
"Some years are going to fool us," he said. It's a roll of the dice to some degree."
Mindful that the forecasts had been off last year, emergency-preparedness officials urged people not to become complacent.
"Last year was easy. There's no reason to believe this year will be anything but tough," said Michael Chertoff, secretary of Homeland Security. "It is a big mistake to count on being lucky."
Reuters contributed to this report.