Note to Editors: The complete forecast, as well as a detailed description of forecast factors, press releases and access to downloadable broadcast-quality audio clips and video clips, will be available on the Web at www.colostate.edu. by 8 a.m. Mountain Time on Aug. 6.
Just days after Alex, the season’s first Atlantic-basin hurricane, brushed the U.S. coastline, William Gray and Philip Klotzbach of the Colorado State University hurricane forecast team issued a report this morning slightly reducing the team’s seasonal forecast. However, the researchers still call for above-average hurricane activity this year and expect slightly above-average tropical cyclone activity in August and September.
As detailed in today’s updated Atlantic seasonal hurricane forecast (August 6), Gray and Klotzbach call for a total of 13 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 slightly from the team’s late May forecast of 14 named storms, eight hurricanes and three intense hurricanes. The long-term average is 9.6 named storms, 5.9 hurricanes and 2.3 intense hurricanes per year.
"Based on atmospheric changes from late May to early August, including an unexpected minor warming of sea surface temperatures in the central Pacific indicating possible weak El-Nino conditions, we have slightly decreased our seasonal hurricane forecast," said Gray. "We expect storm activity in August and September to be above average, however, October is expected to be below average. Overall, we think the 2004 Atlantic basin tropical storm season will be somewhat active and about 125 percent of the long-term average."
The forecasts numbers released in today’s report mirror the team’s December extended-range forecast.
For the third year, Gray and his team are also issuing tropical cyclone activity forecasts for the specific 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, Gray and his team forecast four named storms, three hurricanes and one intense hurricane for the Atlantic basin. For September, the team predicts five named storms, three hurricanes and one intense hurricane. For October, they predict a below-average month.
"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 Philip Klotzbach, an atmospheric science researcher and lead member of Gray’s forecast team. "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, Gray and his team have 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 the first 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. William Gray and Philip Klotzbach of the Colorado State University hurricane forecast team, with assistance from the GeoGraphics Laboratory at Bridgewater State College in Massachusetts, launched the site in June.
As part of today’s updated report, 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 68 percent chance of an intense hurricane hitting somewhere along the U.S. coastline in 2004 (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 48 percent (long-term average is 31 percent). For the Gulf Coast from the Florida Panhandle westward to Brownsville, Texas, the probability is 38 percent (the long-term average is 30 percent). These probabilities are slightly reduced from the team’s late May predictions of 71 percent, 52 percent and 40 percent respectively.
"Even with the slight forecast reduction, we still estimate the probability of a U.S. major hurricane making landfall is higher than normal at about 130 percent of the long term average," said Gray.
Gray believes 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. The last nine years have witnessed 122 named storms, 69 hurricanes and 32 major hurricanes 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.
"Climatology will eventually right itself. We cannot say exactly when or where it will happen, but it will happen and we must expect a great increase in landfalling major hurricanes such as this nation witnessed in previous decades," Gray said. "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."
Gray and his team continuously work to improve their 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://typhoon.atmos.colostate.edu.
Gray and his forecast team will issue seasonal updates of the 2004 Atlantic basin hurricane activity on Sept. 3 and Oct. 1. In addition to Gray and Klotzbach, other team members include William Thorson, Amie Hedstrom and others.