FORT COLLINS, COLO. - William Gray and the Colorado State University hurricane forecast team have slightly increased their predictions for the 2003 hurricane season. In their latest forecast update, issued today before the official beginning of hurricane season on June 1, Gray and his colleagues continue to predict Atlantic basin storm activity to be well above average in 2003. They expect twice as many hurricanes as in 2002 and an increased probability of landfalling hurricanes.
"The dissipation of El Nino and the anticipated formation of a La Nina in the Pacific are factors leading to the increase in our May update of two more tropical storms,” said Gray. “The amount of hurricane activity remains identical to our earlier Dec. 6 and April 4 forecasts. Overall, we anticipate the 2003 Atlantic basin hurricane season to be very active.”
As detailed in today’s update, Gray and his colleagues call for a total of 14 named storms to form in the Atlantic basin this year, two more than the team’s early December and April forecasts. Of the 14 storms, eight 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. The long-term average is 9.6 named storms, 5.9 hurricanes and 2.3 intense hurricanes per year. Last year there were 12 named storms but only four hurricanes and two intense hurricanes formed.
The El Nino in the Pacific, which played a role in suppressing 2002 hurricane activity, has now dissipated. The team foresees La Nina, or cold-water conditions, to be established in the Pacific by the beginning of the most active part of the hurricane season in mid-August. Additionally, the Colorado State forecasters cite anomalously warm sea surface temperatures and lower than normal sea level pressure in the Atlantic as other factors that are expected to contribute to making 2003 an above-average hurricane season.
The Colorado State forecast team also stresses a higher than average probability of at least one intense hurricane making landfall in the United States this year. According to today’s forecast, there is a 69 percent chance of a major hurricane hitting somewhere along the U.S. coastline in 2003 (the 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 49 percent (the long-term average is 31 percent). For the Gulf Coast from the Florida Panhandle westward to Brownsville, the probability is 39 percent (the long-term average is 30 percent). The team also expects an above-average major hurricane landfall risk in the Caribbean.
The last eight years have witnessed 106 named storms, 62 hurricanes and 29 major hurricanes in the Atlantic basin. During that period, only three of the 29 major hurricanes (Opal, Bret and Fran) crossed the U.S. coastline. Based on historical averages, one in three major Atlantic basin hurricanes comes ashore in the United States. Before Lili made landfall as a category 2 hurricane in October 2002, a record 21 consecutive Atlantic basin hurricanes formed without making landfall along the U.S. coast.
"The United States has been very lucky over the past three decades in witnessing very few major hurricanes making landfall in Florida and along the East Coast. At the same time, we have seen large coastal population growth, and many of the people moving to these areas do not realize the potential danger of landfalling hurricanes,” said Gray. “If a major storm hit a populated area such as southeast Florida or Long Island, the results would be devastating. Regardless of whether a major hurricane makes landfall this year, it is inevitable that we will see hurricane-spawned destruction in coming years on a scale many, many times greater than what we have seen in the past."
On a long-term basis, major hurricanes account for about a quarter of all named storms, but when normalized for population, inflation and wealth per capita, they cause about 85 percent of all tropical cyclone-spawned destruction.
The storm seasons spanning 1995-2002 comprised the most active eight consecutive hurricane years on record, and the Colorado State forecasting team believes that we have entered a new multi-decadal cycle of increased hurricane and landfall probability as was witnessed in the 1940s and 1950s.
“Our forecast team believes that we have definitely entered a new era for increased storm activity, particularly an increase in the number of major hurricanes,” said Philip Klotzbach, an atmospheric science researcher and member of Gray’s forecast team. “Particularly along the East Coast, citizens should be prepared for two or three decades of increased major hurricane activity, which also means increased probability of landfalling hurricanes.”
In this new era as in the past, there will be individual years with below-average numbers of hurricanes. According to the team, 1997 and 2002 were years of temporary deviation from the long-period change that started in 1995. The predicted hurricane activity of 2003 is expected to be in line with the global atmospheric and oceanic conditions of this new, more active era.
Gray and his team are continually working to improve their forecast methodologies based on a variety of climate-related global and regional predictors. For the May 30 forecast, the team is using an updated statistical technique based on 52 years of past global information. The new technique is expected to further improve the team’s record of seasonal forecast skill. For a detailed description of the forecast factors, visit the Web at http://typhoon.atmos.colostate.edu.
“We are also performing new research to forecast the month-to-month variability of Atlantic basin hurricane activity and landfall probability,” said Gray. “Our forecast accuracy has been improving in recent years, and we feel ongoing research will add further improvement and understanding.”
The Colorado State forecast team does not attribute changes in recent and projected Atlantic hurricane activity to human-induced global warming.
The team will issue seasonal updates of the 2003 Atlantic basin hurricane activity on Aug. 6, Sep. 3 and Oct. 2. The August forecast will include separate monthly forecasts for August-only, September-only and October-only storm activity.
In addition to Gray, team members include Christopher Landsea, Philip Klotzbach, Eric Blake, William Thorson, Jason Connor and others.