The Colorado State University forecast team today maintained its earlier prediction for the 2006 hurricane season. The U.S. Atlantic basin will likely experience another very active season, but most likely with fewer landfalling intense hurricanes than in 2005 – the costliest, most destructive hurricane season ever.
The team’s forecast for the 2006 hurricane season anticipates 17 named storms forming in the Atlantic basin between June 1 and Nov. 30. Nine of the 17 storms are predicted to become hurricanes, and of those nine, five are expected to develop into intense or major hurricanes (Saffir/Simpson category 3-4-5) with sustained winds of 111 mph or greater.
The 2005 season witnessed 27 named storms, 15 hurricanes and seven intense hurricanes. Long-term averages are 9.6 named storms, 5.9 hurricanes and 2.3 intense hurricanes per year.
The entire report is available on the Web at http://hurricane.atmos.colostate.edu.
"We have maintained our forecast from our early December prediction as the Atlantic Ocean remains anomalously warm and tropical Pacific sea surface temperatures have continued to cool," said Phil Klotzbach of the Colorado State University hurricane forecast team. "We expect either neutral or weak La Ni?a conditions to be present during the upcoming hurricane season."
The hurricane forecast team predicts tropical cyclone activity in 2006 will be 195 percent of the average season. By comparison, 2005 witnessed tropical cyclone activity that was about 275 percent of the average season.
"Even though we expect to see the current active period of Atlantic major hurricane activity to continue for another 15-20 years, it is statistically unlikely that the coming 2006-2007 hurricane seasons, or the seasons that follow, will have the number of major hurricane U.S. landfall events as we have seen in 2004-2005," said Colorado State Professor William Gray.
The hurricane forecast team reiterated its probabilities for a major hurricane making landfall on U.S. soil:
– An 81 percent chance that at least one major hurricane will make landfall on the U.S. coastline in 2006 (the long-term average probability is 52 percent).
– A 64 percent chance that a major hurricane will make landfall on the U.S. East Coast, including the Florida Peninsula (the long-term average is 31 percent)
– A 47 percent chance that a major hurricane will make landfall on the Gulf Coast from the Florida Panhandle west to Brownsville (the long-term average is 30 percent).
The team also predicted above-average major hurricane landfall risk in the Caribbean.
"In any one season, most U.S. coastal areas will not feel the effects of a hurricane no matter how active a season," Klotzbach said. "The probability of landfall for any one location along the coast is very low. However, low landfall probability does not ensure that hurricanes will not come ashore, so coastal residents should always be prepared."
Florida and the Gulf Coast were ravaged by four landfalling hurricanes in each of the past two years. Hurricanes Charley, Frances, Ivan and Jeanne caused devastating damage in 2004 followed by Dennis, Katrina, Rita and Wilma in 2005.
"What made the 2004-2005 seasons so unusually destructive was the high percentage of major hurricanes that moved over the U.S. coastline," Gray said. "These landfall events were not primarily a function of the overall Atlantic basin net major hurricane numbers, but rather of the favorable broad-scale Atlantic upper-air steering currents that were present the last two seasons. It was these favorable Atlantic steering currents that caused so many of the major hurricanes to come ashore."
Probabilities of tropical storm-force, hurricane-force and intense hurricane-force winds occurring at specific locations along the U.S. East and Gulf Coasts within a variety of time periods are listed on the Landfall Probability Web site. The site provides U.S. landfall probabilities 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. Klotzbach and Gray update the site regularly with assistance from the GeoGraphics Laboratory at Bridgewater State College in Massachusetts.
The hurricane team’s forecasts are based on the premise that global oceanic and atmospheric conditions – such as El Ni?o, 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.
For 2006, Gray and the hurricane forecast team expect continued warm tropical and north Atlantic sea-surface temperatures, prevalent in most years since 1995, as well as neutral or weak La Ni?a conditions – a recipe for greatly enhanced Atlantic basin hurricane activity. These factors are similar to conditions that occurred during the 1964, 1996, 1999 and 2003 seasons. The average of these four seasons had well above-average activity, and Klotzbach and Gray predict the 2006 season will have slightly more activity than the average of these four years.
Gray does not attribute changes in recent and projected Atlantic hurricane activity to human-induced global warming.
"Seasonal and monthly variations of sea surface temperature within individual storm basins show only very low correlations with monthly, seasonal and yearly variations of hurricane activity," Gray said.
Klotzbach is the lead author on the team’s seasonal, monthly and landfall probability forecasts. Gray had been at the helm for 22 years.
The team will issue seasonal updates of its 2006 Atlantic basin hurricane activity forecast on May 31, Aug. 3, Sept. 1 and Oct. 3. The August, September and October forecasts will include separate forecasts for each of those months.