June 5th, 2009

North Atlantic Tropical Cyclone Season Forecast 2009

Posted at 1:00 AM ET

The Colorado State University tropical storm research team has further lowered its hurricane development forecast for the 2009 North Atlantic season, and now foresees “below-average activity.” Researchers Philip Klotzbach and William Gray decreased their forecast from their April prediction and now expect 11 named tropical storms to develop in the North Atlantic basin between June 1, 2009 and November 30, 2009. Of these, five are predicted to become hurricanes and two major hurricanes with sustained winds of 111 mph or greater (Category 3 and above on the Saffir-Simpson Scale). In April, the Colorado State University predicted an average season with 12 named storms, six hurricanes and two major hurricanes.

forecast-atlantic-basin-cyclone-development

The latest 2009 forecast was cut because of cooler-than-normal tropical Atlantic sea surface temperatures and the greater potential for a weak El Niño event during the bulk of the hurricane season, Klotzbach said. El Niño, a phenomenon marked by a warming of equatorial Pacific waters, tends to increase levels of vertical wind shear that can prevent the formation of tropical storms. Klotzbach added that tropical Atlantic sea surface temperatures are the lowest they have been since 1994, meaning less fuel for hurricane development.

Klotzbach and Gray said that the chances of at least one major hurricane making landfall in the US in 2009 is 48 percent, lower than the 54 percent predicted in April and below the long-term average of 52 percent. For the US east coast, including the Florida Peninsula, the probability of a major hurricane making landfall is 28 percent, again down from the 32 percent forecast in April and below the average of 31 percent. For the Gulf Coast, from the Florida Panhandle west to Brownsville, the probability is 28 percent, compared with a long-term average of 30 percent. For the Caribbean, meanwhile, Klotzbach and Gray said the probability of a major hurricane passing through the region was 39 percent, down on the long-term average of 42 percent.

The next Philip Klotzbach and William Gray forecast is due to be released on August 4, 2009.

Separately, WSI Corporation also updated their 2009 Atlantic hurricane forecast on 27 May. WSI maintained its forecast from April and predicted 11 named storms, six hurricanes and two major hurricanes will develop in 2009. WSI said the numbers remained the same due to sea surface temperatures in the tropical Atlantic being at their lowest level since 1994. In addition, WSI said wind shear will be slightly above normal due to a trend towards El Niño conditions. The 2009 forecast numbers are relatively close to the long term average (1950-2008) of 9.8 named storms, 6.0 hurricanes and 2.5 major hurricanes, WSI said. WSI added that any future changes to this year’s forecast would likely see lower numbers. Its next hurricane update is scheduled for June 22, 2009.

The North Atlantic tropical cyclone names for 2009 are: Ana, Bill, Claudette, Danny, Erika, Fred, Grace, Henri, Ida, Joaquin, Kate, Larry, Mindy, Nicholas, Odette, Peter, Rose, Sam, Teresa, Victor, Wanda.

Sources: NOAA, Associated Press Newswires, Reuters News, Platts Commodity News, Bloomberg, http://hurricane.atmos.colostate.edu/Forecasts/2009/june2009/jun2009.pdf , WSI Corporation

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