Note to Editors: The complete hurricane forecast, a detailed description of forecast factors, downloadable broadcast-quality audio clips and video clips are available on the Web at www.colostate.edu.
Heading into what is traditionally the busiest three months of the hurricane season, William Gray, Philip Klotzbach and the Colorado State University forecast team have significantly increased their early-season predictions and expect an extremely active hurricane season in 2005. The team today also issued monthly forecasts for August, September and October, and they expect all three of these months to be well above average.
Gray and Klotzbach also continue to call for an above-average likelihood of landfalling hurricanes for the remainder of the hurricane season.
"Based on research data obtained through July, we foresee one of the most active hurricane seasons on record," Gray said. "This is the highest level of hurricane activity we have ever forecast since beginning seasonal hurricane forecasts at Colorado State in 1984."
As detailed in today’s updated Atlantic seasonal hurricane activity forecast (Aug. 5), Gray and Klotzbach call for a total of 20 named storms to form in the Atlantic basin this year. Of these, 10 are predicted to become hurricanes and six are anticipated to evolve into intense hurricanes (Saffir/Simpson category 3-4-5) with sustained winds of 111 mph or greater. The total Net Tropical Cyclone (NTC) activity in 2005 is expected to be about 235 percent of the long-term average. These forecast numbers have been raised from the team’s May 31 forecast of 15 named storms, eight hurricanes and four intense hurricanes. The long-term (1950-2000) average is 9.6 named storms, 5.9 hurricanes and 2.3 intense hurricanes per year.
"This forecast increase is due to a continuing enhancement of favorable tropical cyclone formation conditions," Klotzbach said. "Continued Atlantic Ocean warming, reduced vertical wind shear, low tropical Atlantic sea level pressures, increased West African rainfall and lack of El Nino conditions in the Pacific are some of the strongest factors driving this active season."
Gray and Klotzbach today also issued tropical cyclone activity forecasts for the specific months of August, September and October. These newer monthly forecasts, now in their fourth year, 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, Gray and his team forecast five named storms, three hurricanes and one intense hurricane for the Atlantic basin. For September, the team predicts five named storms, four hurricanes and two intense hurricanes. For October, they predict three named storms, two hurricanes and one intense hurricane. All three of these forecasts are well above the climatological average.
"There are often monthly periods within active and inactive hurricane seasons that do not conform to the overall season, and 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," Klotzbach said. "We are continually improving our forecasts to provide specific monthly hurricane forecasts."
Another significant focus of the Colorado State team’s research involves efforts to develop forecasts of the probability of hurricane landfall along the U.S. coastline. 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 updated forecast, there is a 77 percent chance of an intense hurricane hitting somewhere along the U.S. coastline during the remainder of the 2005 season (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 58 percent (long-term average is 31 percent). For the Gulf Coast from the Florida Panhandle westward to Brownsville, Texas, the probability is 44 percent (long-term average is 30 percent). The team also calls for above-average major hurricane landfall risk in the Caribbean and in the Bahamas.
Gray believes that, until last year, the United States had been very fortunate over the past four decades in witnessing very few major hurricanes making landfall in Florida and along the East Coast. This was due in large part to a combination of past climate signals that did not favor major hurricane development or the tracking of these storms across the United States coastline. There has also been a degree of luck involved, as many major hurricanes have come close to the United States coastline and then veered away.
The last 10 years have witnessed 137 named storms, 77 hurricanes and 38 major hurricanes in the Atlantic basin. During that period – including 2004 when three major hurricanes made landfall – only six of the 38 major Atlantic basin hurricanes crossed the U.S. coastline. Based on historical averages, about one in three Atlantic basin major hurricanes comes ashore in the United States.
"As last year made very clear, and this year has already reemphasized, citizens living along the eastern seaboard should continually be prepared for the possibility of landfalling hurricanes," Gray said.
The storm seasons spanning 1995-2004 comprised the most active 10 consecutive hurricane years on record, and the Colorado State team believes that 2005 will follow this active trend. The forecasters believe that the United States is in a new, multi-decadal era for increased storm activity.
"Our research indicates that the United States has entered an era of increased major hurricane activity which has been reflected in high activity during eight of the last 10 years," Klotzbach said. "We expect this active tropical cyclone era to continue this year and to likely span the next two or three decades."
Along with today’s updated probabilities, Klotzbach has updated the Landfall Probability Web site which provides extensive landfall probabilities for the Gulf and East Coast regions of the United States. In partnership with the GeoGraphics Laboratory at Bridgewater State College, a Web application has been created that displays landfall probabilities for 11 regions, 55 subregions and all 205 coastal and near-coastal counties from Brownsville, Texas, to Eastport, Maine. Probabilities of winds in the area of a subregion and county as well as 50-year probabilities for winds of tropical storm force, hurricane force and intense hurricane force are also provided. The Web page is accessible at http://www.e-transit.org/hurricane. The site can also be accessed from the Colorado State University Tropical Meteorology Project home page at http://hurricane.atmos.colostate.edu/.
The Colorado State forecast team does not attribute changes in recent or projected Atlantic basin hurricane activity to human-induced global warming. These changes in hurricane activity are viewed as resulting from long-period natural climate alterations that historical and paleo-climate records show to have occurred many times in the past.
Gray and Klotzbach will be issuing seasonal updates of their 2005 Atlantic basin hurricane activity forecast on Sept. 2 and Oct. 3.
Gray and Klotzbach continuously work to improve their forecast methodologies based on a variety of climate-related global and regional predictors. For a detailed description of the seasonal and monthly forecast factors, visit the Web at http://hurricane.atmos.colostate.edu/.