Forecasters said this year's gentle hurricane season was attributable to the El Nino phenomenon, a weather pattern created by the warming of tropical Pacific Ocean waters.

"Activity in 2009 was reduced considerably, due largely to the moderate El Nino event that developed," said William Gray, a noted weather forecaster with Colorado State University who has spent more than a quarter-century tracking hurricane activity.

Gray said El Nino "generated significantly stronger-than-average vertical wind shear, especially in the Caribbean and Gulf of Mexico," conditions seen as less-than-ideal for hurricane formation.

During the six-month hurricane season that started on June 1 and ended November 30, there were a total of nine named storms, the fewest since 1997.

Weather officials said the season's three hurricanes were the fewest since 1997.

Of the nine storms, five -- Ana, Danny, Erika, Fred, and Henri -- dissipated harmlessly in the open waters of the Atlantic, Gray said.

Of the season's hurricanes, Ida, which formed in the beginning of November and reached maximum winds of 160 kilometers per hour -- quickly weakened to tropical storm level after making landfall in the southern US state of Alabama.

The season's most powerful hurricane, Bill, packed deadly 217 kilometer (135 mile) per-hour winds, but mostly stayed off shore.

Bill attained category four status on the Saffir-Simpson scale. There were no storms that reached the maximum level-five intensity, officials said.

The relatively gentle hurricane season has been a welcome respite for Caribbean and southeastern US residents still smarting from 2008's pounding.

Last year's hurricane season proved unusually destructive, especially for the island of Cuba, which was struck three times by large, powerful storms.

Haiti also suffered substantial hurricane damage that led to a large loss of life last year, while residents of the southern United States were hit by Hurricanes Fay, Gustav and Ike.

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