Note to Editors: The complete hurricane forecast report and downloadable, broadcast-quality audio clips are available at http://newsinfo.colostate.edu/index.asp. Charts and previous forecasts will be available after 8 a.m. MST at http://hurricane.atmos.colostate.edu.
William Gray and Philip Klotzbach of the Colorado State University hurricane forecast team issued a report today reducing the number of storms expected to form in the Atlantic basin this season.
However, the researchers still call for above-average hurricane activity this year and expect above-average tropical cyclone activity in August and September. That’s despite an average start to the season with two named tropical storms forming in June and July.
Last year at this time, two major hurricanes had formed in the Atlantic basin.
"We’re not reducing the number of hurricanes because we had only two named storms through late July," Gray said. "It’s a general erosion of a number of factors. The tropical Atlantic sea surface temperatures are not quite as warm, tropical Atlantic surface pressure is not quite as low, the eastern equatorial Pacific has warmed some and trade winds in the tropical Atlantic are slightly stronger."
Klotzbach and Gray call for a total of 15 named storms to form in the Atlantic basin this year. Of these, seven are predicted to become hurricanes and three are anticipated to evolve into intense hurricanes (Saffir/Simpson category 3-4-5) with sustained winds of 111 mph or greater. This is down from the team’s late May forecast of 17 named storms, nine hurricanes and five intense hurricanes. The long-term average is 9.6 named storms, 5.9 hurricanes and 2.3 intense hurricanes per year.
"Overall, we think the 2006 Atlantic basin tropical storm season will be somewhat active and about 140 percent of the long-term average," said Klotzbach, an atmospheric science researcher and lead member of Gray’s forecast team. "This year it looks like the East Coast is more likely to be targeted by Atlantic basin hurricanes than the Gulf Coast, although the possibility exists that any point along the U.S. coast could be affected by a hurricane this year."
The Colorado State team on Thursday also issued additional tropical cyclone activity forecasts for the individual months of August, September and October. The monthly forecasts use different parameters than the seasonal forecasts to predict storm activity within shorter time periods and aid with the seasonal predictions.
For the month of August, the team expects four named storms, three hurricanes and one intense hurricane for the Atlantic basin. For September, the team predicts five named storms, three hurricanes and two intense hurricanes. For October, Gray and Klotzbach predict two named storms, one hurricane and no intense hurricanes
"The same factors that make individual months active or inactive are often not the same factors that can make the entire season active or inactive," said Klotzbach. "We are continually improving our forecasts to provide people with specific monthly hurricane forecasts and specific landfall probability forecasts."
Along with today’s updated probabilities, the team has updated the Landfall Probability Web site, which 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.
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 an 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 in 2004.
The Colorado State forecast team continues to warn of the considerably higher-than-average probability of at least one intense (or major) hurricane making landfall in the United States this year. According to today’s forecast, there is a 73 percent chance of an intense hurricane hitting somewhere along the U.S. coastline in 2006 (long-term average is 52 percent). For the U.S. East Coast, including the Florida Peninsula, the probability of an intense hurricane making landfall is 64 percent (long-term average is 31 percent). For the Gulf Coast from the Florida Panhandle westward to Brownsville, Texas, the probability is 26 percent (the long-term average is 30 percent).
Gray said the United States has been fortunate over the past few decades in experiencing only a few major hurricanes making landfall in Florida and along the East Coast. Between 1995 and 2003, 122 named storms, 69 hurricanes and 32 major hurricanes formed in the Atlantic basin. During that period, only three of the 32 major hurricanes – Opal, Bret and Fran – crossed the U.S. coastline. Based on historical averages, about one in three major hurricanes comes ashore in the United States.
But in the past two years, 13 major hurricanes formed in the Atlantic basin – seven of them striking the U.S. coast. Florida and the Gulf Coast were ravaged by four landfalling hurricanes in each of the past two years: In 2004, Hurricanes Charley, Frances, Ivan and Jeanne caused devastating damage followed in 2005 by Dennis, Katrina, Rita and Wilma.
"Last year was an anomaly – for many years, we’re going to be studying why last year was such a freak year," Gray said.
"We’re in this active cycle in the Atlantic basin that is expected to last another 15 to 20 years," he said. "There’s no evidence that storms have gotten worse because the globe has warmed. Unfortunately, with the large coastal population growth in recent decades, we need to anticipate hurricane-spawned destruction in coming years on a scale many times greater than what we have seen in the past."
The team continuously works to improve forecast methodologies based on a variety of climate-related global and regional predictors.
"We are continually making progress 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," said Klotzbach. "Our ongoing forecast research is allowing us to continually improve hurricane prediction skill."
For a detailed description of the many detailed forecast factors, visit the Web at http://tropical.atmos.colostate.edu.
The team will issue seasonal updates of the 2006 Atlantic basin hurricane activity on Sept. 1 and Oct. 3.