By Jane Sutton
MIAMI, Florida (Reuters) - The 2012 Atlantic hurricane season will be "near normal" with nine to 15 tropical storms and four to eight of those will strengthen into hurricanes, the U.S. government weather agency predicted on Thursday.
One to three of those will grow into major hurricanes of Category 3 or higher on the Saffir-Simpson intensity scale, the National Oceanic and Atmospheric Administration said in its seasonal forecast. Major hurricanes have sustained winds of 111 miles per hour or higher and can cause devastating damage.
Hurricane season for the Atlantic Ocean, Caribbean Sea and Gulf of Mexico officially runs from June 1 to November 30, but got off to an early start this year when Tropical Storm Alberto formed off the South Carolina coast last weekend. It turned away and fizzled without threatening land.
Forecasters said pre-season storms are not uncommon and there is not necessarily a connection between an early start and a busy season.
Seasonal forecasts cannot predict whether a specific area might be hit by a storm, but are a useful risk management tool for insurers, commodities traders and energy interests.
Over the last two decades, the average Atlantic season has brought 12 named storms with six hurricanes, including three major hurricanes.
NOAA said the region was still in the midst of a multi-decade active period for hurricanes that began in 1995 but two factors could keep this year's tally near normal.
Hurricanes feed on warm water, but sea surface temperatures in the eastern Atlantic are cooler this year. There is also strong wind shear in the region where most storms form, which tends to squelch storm formation.
Another potentially competing climate factor would be El Nino, a warming of the tropical Pacific that brings wind patterns that can "kill off" Atlantic hurricanes, said Gerry Bell, lead seasonal hurricane forecaster at NOAA's Climate Prediction Center.
"We are right on the threshold of El Nino," said Bell, explaining that forecast models were evenly split on whether El Nino would form this year.
El Nino usually develops in late summer to early fall during the peak months of the season, August to October, which might shift hurricane activity this year to the lower end of the predicted range, Bell added.
El Nino has far-reaching effects on global weather and often brings heavy rain to Pacific islands and the west coast of South America. It is also associated with drought in Australia, Indonesia, the Philippines, Africa and India.
NOAA researchers said they are working on extending current five-day hurricane tracking forecasts to seven days, but those will not be released publicly until NOAA is satisfied that the extended forecast model is as accurate as the five-day forecast.
"That is still a few years away," said Bill Read, who will retire as director of the Miami-based National Hurricane Center on June 1.
NOAA is also experimenting this year with unmanned Global Hawk drones as part of a project aimed at improving tracking and intensity forecasts by 50 percent by 2020. The drones can fly at 60,000 feet and drop devices to measure wind, humidity and temperature into the storm, according to Frank Marks, the director of NOAA's hurricane research division.
Hurricane Hunter P-3 aircraft fitted with Doppler radar and capable of flying into the center of storms now also have satellite capacity to download real-time data more quickly to researchers on the ground for incorporation into forecast models.
(Additional reporting by David Adams; Editing by Vicki Allen)