William Gray and Colorado State University Forecast Team Predict Above-Average Hurricane Activity for 2005

Note to Editors: The complete hurricane forecast report, related research, detailed descriptions of forecast factors and previous forecasts are available on the Web at www.colostate.edu or http://typhoon.atmos.colostate.edu.

Following one of the most intense and destructive hurricane seasons on record, William Gray, Philip Klotzbach and the Colorado State University forecast team predict above-average Atlantic basin hurricane activity again in 2005, but the team does not expect the large number of intense hurricanes or landfalling storms seen in 2004.

Gray and his team released their first extended-range forecast for the 2005 hurricane season today, Dec. 3, and anticipate that 11 named storms will form in the Atlantic basin between June 1 and Nov. 30. Six of the 11 storms will become hurricanes, and of those six, three are expected to develop into intense, or major, hurricanes (Saffir/Simpson category 3-4-5) with sustained winds of 111 mph or greater. Long-term averages are 9.6 named storms, 5.9 hurricanes and 2.3 intense hurricanes per year. The 2004 season witnessed 15 named storms, nine hurricanes and six intense hurricanes.

The entire report is available on the Web at http://typhoon.atmos.colostate.edu.

"We believe that 2005 will continue the trend of enhanced major hurricane activity in the Atlantic basin that we have seen over the past 10 years, and we expect this active hurricane era to span the next two or three decades," Gray said. "Our in-depth analysis of current and projected global atmospheric and oceanic predictors through November indicates that the 2005 Atlantic basin hurricane season will be an active one with tropical cyclone activity about 115 percent of the average season."

In comparison, 2004 witnessed tropical cyclone activity 233 percent of the average season.  This is twice what they are projecting for the 2005 season.  

Gray and his team also predict a higher than average probability in 2005 for a major hurricane making landfall on the U.S. and Caribbean coastlines. According to today’s report, there is a 69 percent chance of at least one major hurricane hitting somewhere along the U.S. coastline in 2005 (the long-term average probability is 52 percent). For the U.S. East Coast, including the Florida Peninsula, the probability of an intense hurricane making landfall is 49 percent (the long-term average is 31 percent). For the Gulf Coast, from the Florida Panhandle west to Brownsville, the probability is 39 percent (the long-term average is 30 percent).

"Although Floridians should not expect what they experienced in terms of landfalling hurricanes in 2004 to be the norm for this upcoming season or future years, they, and everyone living along the U.S. East Coast, should always be prepared for the possibility of hurricanes making landfall, especially during this era of increased hurricane activity," Gray said.

In 2004, Florida and the Caribbean islands were ravaged by four landfalling hurricanes, three of which were major storms. Hurricanes Charley, Frances, Jeanne and Ivan caused devastating damage in Florida. Although not technically making U.S. landfall, Hurricane Alex caused damage along the Outer Banks of North Carolina, and Hurricane Gaston caused some damage in South Carolina. In addition, tropical storms Bonnie, Hermine, Ivan and Matthew made landfall along the U.S. coastline in 2004.  This ties a record for most U.S. landfalling tropical cyclones in a single season.  

"It is not the number of hurricanes in the Atlantic basin that was so unusual in 2004, but rather the rare combination of high major hurricane formation and very favorable hurricane steering conditions that drove so many storms from the deep tropics across the Caribbean and into Florida," Klotzbach said. "We do not anticipate this same optimal combination of hurricane formation and steering conditions to be present in 2005.  Next year’s landfall numbers are likely to be significantly less than what occurred in 2004."

Along with today’s report, the team has updated the Landfall Probability Web site that provides probabilities of tropical storm-force, hurricane-force and intense hurricane-force winds making landfall in specific locations along the U.S. East and Gulf Coasts within a variety of time periods. U.S. landfall probabilities are available for 11 regions, 55 sub-regions and 205 individual counties along the U.S. coastline from Brownsville, Texas, to Eastport, Maine. The Web site, available to the public at www.e-transit.org/hurricane, is the first publicly accessible Internet tool that adjusts landfall probabilities for regions, sub-regions and counties based on the current climate and its projected effects on the upcoming hurricane season. Gray and Klotzbach, with assistance from the GeoGraphics Laboratory at Bridgewater State College in Massachusetts, launched the site last June.

The hurricane team’s forecasts are based on the premise that global oceanic and atmospheric conditions – such as El Nino, sea surface temperatures and sea level pressure – that preceded active or inactive hurricane seasons in the past provide meaningful information about similar trends in future seasons.  

Currently observed conditions include anomalously warm tropical and north Atlantic sea-surface temperatures as well as weak El Nino conditions. These factors are similar to conditions that occurred in the fall before the 1952, 1958, 1970 and 2003 seasons. The average of these four seasons had slightly above-average activity. Gray and the hurricane forecast team predict El Nino conditions will remain neutral to slightly warm and that the warm sea-surface temperatures in the north and tropical Atlantic that have been prevalent in most years since 1995 will continue.

Gray and his research team are continually improving their forecast techniques based on a wide variety of global and regional atmospheric and oceanic predictors. Gray, in his 22nd year of forecasting Atlantic basin hurricanes, believes recent improvements in the gathering, archival and data analysis techniques of global atmospheric and oceanic signals can be used to consistently improve forecasts of Atlantic basin hurricane activity and landfall probabilities.

"We are continually making progress in better understanding and in improving statistical hurricane forecasting techniques and in better understanding why there is such variability in month-to-month and year-to-year Atlantic basin hurricane activity," Gray added. "Our ongoing forecast research is allowing us to continually improve hurricane prediction skill."

Gray does not attribute changes in recent and projected Atlantic hurricane activity to human-induced global warming.      

Gray and Klotzbach will be issuing seasonal updates of their 2005 Atlantic basin hurricane activity forecast on April 1, May 31, Aug. 5, Sept. 2 and Oct. 3. The August, September and October forecasts will include separate forecasts for each of those months.