The number of tropical storms and hurricanes expected to form in the Atlantic Basin this year will be slightly lower than both long-term and short-term historical averages, according to forecasters at Andover, MA-based Weather Services International (WSI).

The WSI forecast team expects 11 named storms in the Atlantic Basin this year, including six hurricanes, two of them major hurricanes (Category 3 or higher). That would be slightly lower than the 1950-2011 average of 12 named storms, seven hurricanes and three major hurricanes and the 1995-2011 average of 15/8/4, WSI said. It would also be a slightly less active 2012 Atlantic hurricane season than the one expected by forecasters at Colorado State University (CSU), who recently said they expect 10 named storms this year, including four hurricanes, two of them major hurricanes (see Daily GPI, April 16).

And it would be significantly less tropical activity than was observed in 2010 or 2011. While last year’s Atlantic hurricane season didn’t bring many tropical storms to Gulf of Mexico energy interests or the North American mainland, it did produce the third-highest number of tropical storms since records began in 1851 and continued a trend of active hurricane seasons begun in 1995 (see Daily GPI, Nov. 29, 2011).

“The combination of much cooler North Atlantic ocean temperatures and a trend towards El Nino conditions suggest a notable reduction in activity,” said WSI Chief Meteorologist Todd Crawford. “There is still uncertainty regarding the development of El Nino, which will impact future forecast updates. If the chances of El Nino development increase, our forecast numbers will likely go down even further in future updates.”

With more than a month to go until the 2012 Atlantic hurricane season officially begins on June 1, WSI said there is no particularly strong hurricane landfall signal.

“After a three-year respite for the U.S. coastline, Hurricane Irene moved ashore along the East Coast during late August 2011 [see Daily GPI, Aug. 30, 2011]. Irene was a wake-up call after a historically unusual lull in hurricane landfalls,” Crawford said. “For 2012, our landfall model depicts slightly below-normal probabilities of landfall from Florida and up the East Coast, with slightly above-normal probabilities in the Gulf. This is reflective of the general lack of atmospheric blocking in the North Atlantic (also known as the positive phase of the North Atlantic Oscillation) that we expect.”

The CSU team in its recent forecast said it expected a below-average probability for major hurricanes making landfall along the United States coastline and in the Caribbean. There is a 24% probability of a major hurricane making landfall on the Gulf Coast from the Florida panhandle west to Brownsville, TX; a 24% probability of a major hurricane making landfall on the East coast; and a 42% probability of major hurricane coming ashore anywhere on the U.S. coastline — all below the average over the last century — the CSU forecasters said. The probability of at least one major hurricane entering the Caribbean is 34%, compared to 42% for the last century.

WSI is scheduled to issue its next tropical storm forecast on May 23.

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