WASHINGTON (Reuters) - The 2011 Atlantic hurricane season will be "above normal", spawning six to 10 hurricanes of which around half could become major, the government's weather agency forecast on Thursday.
However, as the 2010 season showed -- it was very active but the U.S. coastline escaped a hit -- a high frequency of storms does not always translate into more destructive landfalls.
In its first forecast for the season that begins on June 1, the National Oceanic and Atmospheric Administration (NOAA) anticipated 12 to 18 named storms, a somewhat lower level of activity than the 2010 Atlantic hurricane season.
Six to 10 of those storms were seen developing into hurricanes, of which three to six could become major at Category 3 or above, with winds of more than 110 miles per hour (177 km per hour), the agency said.
"NOAA's forecast team is calling for an above-normal season this year," NOAA Administrator Jane Lubchenco told a news conference outside the agency's Satellite Operations Facility.
But she added NOAA's forecasting capacity could not yet pinpoint where or when a hurricane would hit: "This hurricane outlook does not make any predictions about landfall, either place or timing".
The briefing took place under a light rain shower.
NOAA's 2011 outlook mirrored earlier predictions from private forecasters calling for an active hurricane season this year.
The hurricane season officially starts on June 1 and typically peaks between late August and mid-October. An average Atlantic hurricane season brings 11 tropical storms with six hurricanes, including two major hurricanes, NOAA said.
The 2010 season produced 19 named storms, tying for the third most active season with 1887 and 1995, according to the U.S. National Hurricane Center. Twelve storms grew into hurricanes, tying with 1969 for the second most active season in that category.
The activity last year was in line with NOAA's spring 2010 forecast that called for 14 to 23 named storms, with eight to 14 developing into hurricanes.
But no hurricane made U.S. landfall last year. "This year we are unlikely to see a repeat of last year, where there were a total of 19 named storms ... Despite this tropical onslaught, most of the tropical storms and all of the hurricanes last year fortunately avoided U.S. coastlines, " Lubchenco said.
"We cannot count on having the same luck this year," she said.
Lubchenco said the La Nina weather phenomenon, whose conditions generally contribute to storm development in the Atlantic-Caribbean basin, was weakening but its influence should continue at least into the early summer.
"La Nina, which continues to weaken in the equatorial Pacific Ocean, is expected to dissipate later this month or in June, but its impacts such as reduced wind shear are expected to continue into the hurricane season," NOAA's forecast said.
Wind shear, the shifting of winds at various levels in the atmosphere, impedes the formation of hurricanes.
Forecasts are being closely watched by energy analysts and oil producers this year with oil prices holding over $100 a barrel and consumers paying more than $4 a gallon at the pump.
If a hurricane approaches U.S. offshore energy installations in the Gulf of Mexico, a major storm can pose a threat to about one-quarter of U.S. oil production and about 10 percent of natural gas output.
NOAA had accurately predicted that last year would be the busiest since the record-shattering 2005 season, when Hurricane Katrina killed more than a thousand people and wreaked havoc with energy production in the Gulf of Mexico.
But neither NOAA nor any private forecaster foresaw that the successive 2010 storms would entirely miss the U.S. coast. Even at their most accurate, pre-season forecasts can only estimate the number of storms, not the precise paths.
The U.S. coast has been spared a direct hit since 2008.
Nearly 37 million people -- one in eight U.S. residents -- live in the coastal region most at risk for hurricanes, from North Carolina to Texas, according to the U.S. Census Bureau.
Additional reporting by Jane Sutton in Miami, Editing by Pascal Fletcher and Dale Hudson