Note to Editors: The full verification report and a chart wrapping up the season are available with the news release at http://www.newsinfo.colostate.edu/ and at http://hurricane.atmos.colostate.edu/. The 53-page verification includes an extensive discussion of the climate features that likely caused the 2008 Atlantic basin hurricane season to behave the way it did.
Colorado State University’s hurricane forecast team accurately predicted a well above-average hurricane season for the Atlantic basin for 2008, according to its seasonal verification report issued today.
The report summarizes tropical cyclone activity in the Atlantic basin during the 2008 hurricane season and compares the team’s seasonal and monthly forecasts to what actually occurred.
The Colorado State team of Phil Klotzbach and William Gray made its long-range seasonal forecast, which called for an above-average hurricane season, on Dec. 7, 2007 and issued seasonal updates on April 8, June 3, and Aug. 5. On April 8 and on June 3, just as hurricane season began, the team called for 15 named storms, eight hurricanes and four major (Cat 3-4-5) hurricanes. The team upgraded their prediction to 17 named storms, nine hurricanes and five major hurricanes on Aug. 5.
Observed were 16 named storms, eight hurricanes and 5 intense hurricanes.
The team bases its annual forecasts on 60 years of previous data that includes such factors as Atlantic sea surface temperatures and sea level pressures, levels of vertical wind shear (the change in wind direction with height), and El Nino.
"We consider our April and June forecasts to have been especially successful," said Klotzbach. "We believed that given the extremely active early season and the climate parameters observed up to August that the remainder of the season was likely to be slightly more active than it was. The rest of the season had activity at above average levels, with both Gustav and Ike both causing tremendous amounts of devastation in the United States and in the Caribbean."
"Landfall probabilities for the 2008 hurricane season were estimated to be well above their climatological averages due to our prediction for an active season," Gray said. "The 2008 hurricane season was very active from a U.S. landfall perspective, with three tropical storms and three Category 2 hurricanes making U.S. landfall this year: Hurricane Dolly, Tropical Storm Edouard, Tropical Storm Fay, Hurricane Gustav, Tropical Storm Hanna and Hurricane Ike."
On average, the United States experiences approximately 3.6 named storms, 1.9 hurricanes, and 0.7 major hurricane landfalls per year. Although no major hurricanes made landfall in 2008, two storms made landfall at just below major hurricane status (Gustav and Ike at 95 knots). It is estimated that more than $20 billion dollars in total damage was incurred in the United States during the 2008 hurricane season.
"The year was one of the most destructive years on record from a damage perspective," Klotzbach said.
The Atlantic has seen a very large increase in major hurricanes during the 14-year period of 1995-2008 (average 3.9 per year) in comparison with the prior 25-year period of 1970-1994 (average 1.5 per year). This upturn in Atlantic major hurricanes is primarily a result of natural multi-decadal variability in the strength of the Atlantic thermohaline circulation and a concomitant increase in tropical Atlantic sea surface temperatures. These changes are not directly related to global sea surface temperature increases or atmospheric CO2 concentrations.
Highlights of the 2008 season:
-Sixteen named storms formed during the 2008 season. Since 1995, 13 of the last 14 seasons have had more than the 1950-2000 average of 10 named storms. Since aircraft reconnaissance began in 1944, only 2005 (28 named storms), 1995 (19 named storms) and 1969 (18 named storms) have had more named storm formations than 2008.
-No Category 5 hurricanes developed in 2008. This is only the second year since 2002 with no Category 5 hurricanes in the Atlantic. 2006 also had no Category 5 hurricanes.
-July 2008 was especially active. Three named storms, two hurricanes and one major hurricane formed during the month. Since 1944, only 1966, 1995, 1997 and 2005 had more named storm formations in July. Since 1944, only 1966 and 2005 had more hurricane formations. Since 1944, only 2005 had multiple major hurricane formations (Dennis and Emily) during July.
-Three hurricanes made landfall along the U.S. Gulf Coast. This is the most U.S. landfalls since 2005 in the Gulf, which witnessed four landfalls. Prior to 2005, the previous year with three or more U.S. hurricane landfalls in the Gulf was 1985 which also had four hurricane landfalls.
-No major hurricanes made U.S. landfall this year. Following seven major hurricane landfalls in 2004-2005, the United States has not witnessed a major hurricane landfall in the past three years.
-Six named storms in a row (Dolly through Ike) made U.S. landfall. This breaks the old record of five named storms in a row which occurred in 1971, 1979, 1985, 2002, and 2004.
-Hurricane Ike was estimated to cost approximately $8 billion dollars in insured damage. This makes Ike the fifth most damaging inflation-adjusted hurricane in U.S. history.
The team will issue its first forecast for the 2009 hurricane season on Dec. 10.