Government forecasters on Thursday lowered their outlook for the rest of the Atlantic hurricane season after a quiet start with no named storms in the first two months of the six-month stretch.
The National Oceanic and Atmospheric Administration said it expects a near-normal to below-normal season with fewer named storms. The update to NOAA's May forecast comes after the climate pattern El Nino developed over the Pacific Ocean, acting as a damper to tropical storms in the Caribbean and neighboring Atlantic.
But forecasters at NOAA's National Hurricane Center warned people to remain vigilant because the peak period for hurricanes runs from this month through October. The overall season lasts from June through November.
The updated forecast calls for seven to 11 named tropical storms, down from a range of nine to 14 in the May forecast.
Three to six storms could become hurricanes, down from four to seven in the earlier forecast. The new projection says one or two hurricanes could become major storms, instead of one to three major hurricanes.
Tropical storms get names when sustained wind speeds reach 39 mph. They become hurricanes when sustained winds reach 74 mph. Major hurricanes blow at 111 mph or more. The strongest hurricanes are labeled Category 5, with winds greater than 155 mph.
Researchers at Colorado State University also have lowered their forecast for the Atlantic season to 10 named storms, including four hurricanes, two of them major.
The El Nino warming of the Pacific sea surface suppresses storm formation, said lead seasonal hurricane forecaster Gerry Bell.
"El Nino produces stronger upper-level westerly winds over the Caribbean Sea and tropical Atlantic Ocean, which help to reduce hurricane activity by blowing away the tops of growing thunderstorm clouds that would normally lead to tropical storms," Bell said.
Competing with El Nino, however, are conditions that mark an ongoing high-activity era that began in 1995, forecasters said. Those factors include enhanced rainfall over West Africa and warmer Atlantic water temperatures, which favor storm development.
"By no means do we expect the season to be dead," Bell said.
Hurricanes have struck the U.S. during previous El Ninos, including Camille in 1969, a Category 5 storm, Betsy in 1965, Bob in 1991 and Lili in 2002.
So far this year, one tropical depression formed off Cape Hatteras, N.C., on May 28, four days before the official start of the season; it quickly fizzled and never threatened land.
A calm start doesn't mean the rest of the season will stay quiet, forecasters warned. The first storm of the 1992 season — a below-normal year — did not form until late August. But Hurricane Andrew leveled parts of South Florida when it roared ashore as a Category 5 storm.
The 2004 season also had a slow start. By the time it was over, Florida alone had suffered strikes from four separate hurricanes, one of which also caused 3,000 deaths in Haiti.
"It only takes one storm to put a community at risk," said Federal Emergency Management Agency Administrator Craig Fugate. "That is why we need to take action and prepare ourselves and our families before the next storm hits, including developing a family disaster plan."
The first storm of this year in the Atlantic, Caribbean or Gulf of Mexico will be named Ana, followed by Bill, Claudette and Danny.
By this time last year, there had been five named storms, including two hurricanes. In all of 2008, there were 16 named storms, including eight hurricanes. About 1,000 people lost their lives, mostly in flash flooding in the Caribbean.
Gas prices spiked last summer when hurricanes Gustav and Ike slammed into the nation's energy complex in the Gulf of Mexico.
In the Pacific, six named storms, including three hurricanes, have developed so far this year. Hurricane Felicia, a Category 4 storm, was expected to weaken Thursday as it moves over colder water far out in the Pacific. Meanwhile, Tropical Storm Enrique maintained its strength with sustained winds near 50 mph about 1,035 miles west of the southern tip of Baja California.