May 16 (Bloomberg) -- The Atlantic Ocean hurricane season this year will be more active than normal, with as many as five major hurricanes, following last year's historic season when four of the storms hit Florida, U.S. government forecasters said.

The June-through-November season will have 12 to 15 named storms, including seven to nine hurricanes, officials at the National Oceanic and Atmospheric Administration said today at a press conference in Bay St. Louis, Mississippi.

``Forecaster confidence that this will be an active hurricane season is very high,'' Conrad C. Lautenbacher, undersecretary of commerce for oceans and atmosphere, said in a statement. NOAA is part of the U.S. Commerce Department.

The above-average season is expected to continue a trend that began in 1995 and reached a peak last year when Hurricanes Charley, Frances, Ivan and Jeanne wrought more than $20 billion in U.S. property damage and brought down offshore oil and gas platforms in the Gulf of Mexico.

Every year since 1995 has topped average, except 1997 and 2002. Three to five of the hurricanes that develop this year in the Atlantic are expected to make major status, meaning sustained wind speeds of 111 mph (179 Kilometers per hour) or more, the forecasters said.

Forecasters at the National Hurricane Center in Miami pointed to above-average ocean temperatures in the Atlantic and weak El Nino conditions in the eastern Pacific as helping to set up another strong Atlantic tropical-storm season.

`Intense'

``Whenever the (Atlantic) water temperatures are above average, we tend to have above-average tropical cyclone activity,'' said Stacy Stewart, a hurricane specialist at the Miami center. ``And they tend to be intense.''

Neutral to weak El Nino conditions, in place a year ago, favor a strong Atlantic season because such conditions set up wind patterns that go with, rather than against, tropical systems.

``You want the upper-level winds moving in the same direction as your tropical disturbance,'' Stewart said. ``You tend to get that when we have weak or neutral El Nino conditions.''

El Nino refers to the warming of ocean surfaces off the western coast of South America. The phenomenon affects the jet stream, alters storm tracks and creates unusual weather patterns.

Last year's season had eight hurricanes out of a total of 15 named storms. Six storms developed into major hurricanes. A typical hurricane season in the Atlantic produces about 10 tropical storms, six hurricanes and two to three major hurricanes, Stewart said.

Arlene, Ophelia, Wilma

Names selected for this year's crop of storms include Arlene, Gert, Ophelia, Philippe and Wilma. Only storms of tropical-storm strength, defined by sustained wind speeds of at least 39 miles an hour, are named.

Storms become hurricanes when their wind speed tops 73 mph. Scientists use the five-category Saffir-Simpson scale to grade hurricanes. The strongest hurricanes carry winds of 155 mph or more. Major hurricanes register Category 3 to Category 5 on the scale.

``To have another year of multiple hurricanes hitting Florida would be extremely unlikely,'' said Robert Muir-Wood, chief research officer at Newark, California-based Risk Management Solutions Inc. ``We expect to see, on average, $5 billion in losses each year. That would be an average of one to two storms making landfall as hurricanes.''

Allstate

The four hurricanes that lashed Florida last year cost Allstate Corp., the second-largest U.S. auto and home insurer, $2 billion before taxes. The company plans to spend about $100 million more this year on reinsurance policies to limit its losses from potential storms.

Colorado State University scientists also predicted an active year in 2005. The Fort Collins-based team, headed by William Gray and Philip Klotzbach, projected 13 named storms this year and seven hurricanes in an outlook released last month.

The pattern toward more active hurricane seasons, fueled by warmer-than-normal Atlantic Ocean temperatures, may last for another 20 years, Stewart said. It typically takes 30 to 40 years for the ocean to cool down after a period of above-average warmth, he said.

The last active period in the Atlantic was from the mid-1930s to the mid-1960s, Stewart said.

``During these more active periods, we have more hurricane landfalls and more major hurricane landfalls, especially along the east coast of the U.S.,'' he said.

Even during periods of relative inactivity, intense storms can strike. The period from the mid-1960s to the mid-1990s, considered a quiet one among hurricane researchers, spawned Hurricane Camille in 1969, Gilbert in 1988, Hugo in 1989 and Andrew in 1992.

To contact the reporter on this story: Geoffrey Smith in New York at gsmith15@bloomberg.net.

Last Updated: May 16, 2005 13:25 EDT