Researchers predict hurricane-heavy 2003

Fort Collins, CO – Following a suppressed 2002 hurricane season, renowned Colorado State University tropical storm researcher William Gray and his forecast team predict Atlantic basin hurricane activity to be well above average in 2003 – including twice as many hurricanes as in the previous year.

For their first extended-range forecast for 2003, Gray and his colleagues predict that 12 named tropical storms will form in the Atlantic basin between June 1 and Nov. 30. Of these, eight will 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 tropical storms, 5.9 hurricanes and 2.3 intense hurricanes per year. 2002 witnessed 12 named storms but only four hurricanes and two intense hurricanes.

“Information we have obtained and analyzed through November indicates that 2003 will be an active Atlantic hurricane season with above-average activity,” said Gray. “We expect Atlantic basin tropical cyclone activity to be about 140 percent of average this upcoming year.”

The team’s forecast, released Dec. 6, said that an analysis of current and projected global climate signals indicates that Atlantic tropical cyclone activity should be more active than normal during 2003.

According to Gray, the increased activity is due in large part to a predicted termination of current El Nino conditions and an anticipation of warm sea surface temperatures in the north and tropical Atlantic. A moderate El Nino and uncharacteristically cool temperatures in the tropical Atlantic helped to inhibit hurricane activity in 2002.

Gray and his team also call for an increased probability of at least one intense hurricane making landfall in the United States in 2003. “The probability of a major hurricane making U.S. landfall in 2003 is 30 percent higher than in the average season,” said Gray.

According to the forecast, there is a 68 percent chance of a major hurricane hitting somewhere along the U.S. coastline in 2003 (the last century’s average probability was 52 percent). For the U.S. East Coast, including the Florida Peninsula, the probability of an intense hurricane making landfall is 48 percent. For the Gulf Coast – from the Florida Panhandle west to Brownsville – the probability is 38 percent.

The last eight years have witnessed 106 named storms, 62 hurricanes and 29 major hurricanes in the Atlantic basin. During that period, only four of the 29 major hurricanes (Opal, Bret, Fran and Lili) crossed the U.S. coastline. Based on historical averages, one in three major hurricanes comes ashore in the United States. Before Lili made landfall in October 2002, a record 21 consecutive Atlantic basin hurricanes did not make shore along the U.S. coast.

“The United States has been extremely lucky over the past eight years, but climatology will eventually right itself and we must expect a great increase in landfalling intense hurricanes,” said Gray. “With such large coastal population growth in recent decades, it is inevitable that we will see hurricane-spawned destruction in coming years on a scale many times greater than what we have seen in the past.”

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 are in a new multi-decadal era for increased storm activity such as occurred in the 1940s and 1950s. They add that, in this new era as in the past, there will be individual years with below-average numbers of hurricanes. According to the team, 2002 was one of those temporary deviations from the long-period average.

For the Dec. 6 forecast, Gray and his research team are using a recently developed six-to-11 month statistical forecast system based on 51 years of past storm season data. The new system, which provides strong statistical relationships for climate data, is expected to improve extended-range forecasts. For a detailed description of the forecast factors, visit the Web at http://typhoon.atmos.colostate.edu/forecasts.

“Our evolving forecast techniques are based on a wide variety of climate-related global and regional predictors previously shown to be related to forthcoming seasonal Atlantic tropical cyclone activity and landfall probability,” said forecast team member Philip Klotzbach. “This forecast is based on atmospheric and oceanic conditions similar to what is currently observed and what we anticipate to be in place throughout the 2003 hurricane season.”

Gray, in his 20th year of forecasting Atlantic basin storms, believes that these and other recent improvements in the gathering, archival and data analysis techniques of global atmospheric and oceanic signals can be used to continually improve forecasts of Atlantic basin hurricane activity and landfall probabilities.

“Overall, we are making very good progress on 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 Gray. “We feel our ongoing forecast research is allowing us to continually improve hurricane prediction skill.”

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 basic hurricane activity forecast on April 4, May 30, Aug. 7 and Sep. 3. The August forecast will include separate monthly forecasts for August-only and September-only activity.

In addition to Gray and Klotzbach, team members include Christopher Landsea, John Sheaffer and others.