William Gray and Colorado State Team Issue Monthly Hurricane Forecast for September and October, Report Perfect August Forecast

Note to Editors: The complete update, including a forecast total chart and the new September and October monthly forecasts, is available on the Web at http://typhoon.atmos.colostate.edu.

Following an August-only forecast that was right on the mark, William Gray and the Colorado State University hurricane forecast team today issued monthly predictions for September and October as well as a seasonal forecast update. The team’s new September-only forecast calls for four named storms, two hurricanes and one major hurricane. Their October-only forecast calls for three named storms, two hurricanes and one major hurricane.

Overall, Gray and his colleagues keep their seasonal Atlantic basin forecast about the same compared their Aug. 6 update and maintain their call for an above-average season. For the entire 2003 hurricane season, Gray and his team call for 14 named storms (the same as the August forecast), seven hurricanes (down from eight in August) and three major hurricanes (the same as the August forecast.) The long-term average is 9.6 named storms, 5.9 hurricanes and 2.3 intense hurricanes per year. The entire detailed report is available online at http://typhoon.atmos.colostate.edu.

For August, Gray and his colleagues had forecast three named storms, one hurricane and one intense hurricane for the Atlantic basin, which is exactly what occurred. Gray credits this success in large part to former student Eric Blake, whose research efforts as a graduate student helped develop the forecast scheme used for the August 2003 forecast.

"Eric’s forecast scheme showed near-perfect results for this August," said Gray. "A forecaster could never hope to get any better than this."

Team member Phil Klotzbach recently developed schemes to forecast September and October-only hurricane activity. This is the second year that Gray and his team are issuing storm activity forecasts for September and the first time for October. The monthly forecasts use different predictors than the seasonal forecasts. The monthly forecasts also aid with the seasonal predictions.

"The same factors that can 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 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."

Gray and Klotzbach recently developed a methodology for calculating the probability of landfall along the entire U.S. coastline on a one-month basis and are providing monthly-only U.S. hurricane landfall probabilities for September and October.

For September, the estimated probability of at least one hurricane making landfall along the U.S. coastline is 56 percent; for October, the probability is 21 percent. The probability of at least one major hurricane (Saffir/Simpson category 3-4-5) crossing the U.S. coastline is 33 percent for September and 14 percent for October. Gray warns that probabilities for landfalling hurricanes for the remainder of the season are slightly above average.

"We expect storm activity in September to be about average and October to be more active than normal," said Gray. "Overall, we think the remainder of the 2003 Atlantic basin storm season will be slightly above average, leaving the entire season about 130 percent of the average year."

William Gray and his Colorado State colleagues have issued seasonal hurricane forecasts for the past 20 years. The forecasts, issued in early December of the prior year as well as April, June and August, have steadily improved through continuing research. The Colorado State forecasts now include individual monthly predictions and seasonal updates of Atlantic basin storm activity and hurricane landfall probabilities issued in early August, September and October.

The research team will issue another seasonal summary update and outlook for the 2003 Atlantic basin hurricane activity on Oct. 2. In addition to Gray, team members include Philip Klotzbach, William Thorson, Jason Connor and others.