P!N Points: Early look at hurricane season sees fewer extremes, greater chance of landfall

The 2010 Atlantic hurricane season earned notoriety for its high level of activity, which included a stretch of 36 days with a named storm moving through the Caribbean or near the U.S. East Coast. This year’s hurricane season, which begins June 1, is expected to meet the relatively high activity of seasons across the past decade, though it isn’t expected to reach the levels of activity or destruction seen in 2005 or 2010.

In late April, Weather Services International updated its forecast for 2011 to predict a total of 15 named storms, eight hurricanes and four classified as major hurricanes (Category 3, 4 or 5 on the Saffir-Simpson Scale). This was adjusted downward from the original prediction in December of 17 named storms, nine hurricanes and five major hurricanes. Cooling Atlantic sea surface temperatures and a weakening of a La Nina event caused the deduction in the number of storms predicted.

Colorado State University’s annual December forecast predicted 16 named storms, nine hurricanes and five major hurricanes. Forecasts deal with the predicted level of activity of tropical storms and hurricanes, not their exact paths and impacts.

CSU’s forecast makes predictions about the likelihood of a major hurricane making landfall in any U.S. coastal area (73 percent), the East Coast and eastern Florida (49 percent) and the Gulf Coast (48 percent). The latter two predictions are significant departures for the landfall frequency in the last century (31 percent and 30 percent, respectively). The study’s authors predict that the chance of a major hurricane tracking into the Caribbean is 62 percent.

In 2010, the Atlantic basin saw 19 named storms, 12 of which became hurricanes (five of those were major hurricanes). This is a notable increase from the averages over the last 40 years – according to the Weather Channel, between 1966 and 2009, the average Atlantic hurricane season had 11 named storms, six of which were hurricanes (two of those being major hurricanes).

Of the 2010 storms, none of the hurricanes made landfall in the United States, though Tropical Storm Nicole led to deaths in North Carolina.

While the number of predicted storms is fewer than those experienced in 2010, this year’s storms are expected to have a greater impact on the U.S. coastline. Because no hurricanes have made landfall in the United States since 2008, Weather Services International predicts landfall will occur more often this year, with two or three along the Gulf Coast of the United States.

Sea surface temperatures in the Gulf of Mexico and Caribbean are warmer than usual this year, contrasting with Atlantic waters. According to the WSI report, more hurricanes are expected in the Gulf and Caribbean than along the U.S. East Coast as a result of the temperature difference. Storms in 2011 will likely develop closer to South America than near Africa, resulting in a greater chance of landfall in the southern United States.

WSI compares this season to 2008, which was the third costliest on record and included Hurricanes Gustav, Hanna and Ike.

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