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CSU Forecasters Warn of Above-Average Hurricane Activity Yet to Come

While the country continues to focus on the devastation left in the wake of Hurricane Katrina, top storm forecasters William Gray and Philip Klotzbach of the Colorado State University (CSU) hurricane forecast team, warned on Friday that the nation is not out of the woods yet, adding that new methodology for the calculation of onshore hurricane landfalls show that September and October could very well bring more mayhem to Florida and the Gulf Coast.

Since its inception, the forecasting of storms and hurricanes has helped cut down on the loss of life. 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 team said it has recently developed a methodology for calculating the probability of hurricane landfall along the entire U.S. coastline -- specifically for the months of September and October.

According to Friday's report, there is a 43% chance of an intense hurricane hitting somewhere along the U.S. coastline in September (long-period average is 27%). For October, there is a 15% chance (long-period average is 6%).

Noting that it is currently only the halfway point of the 2005 hurricane season, Gray and Klotzbach said that following one of the most active early storm seasons on record, Hurricane Katrina has caused the "greatest economic loss" ever inflicted by a hurricane on the United States, and the probability of more hurricanes remains high.

In fact, Gray and Klotzbach are calling for an above-average likelihood of landfalling hurricanes for the remainder of the hurricane season. "Unfortunately, we are continuing the bad news by predicting above-average activity for September and October," said Gray. "This will be one of the most active seasons and is already the most destructive hurricane season on record."

According to the forecasters' research data through August, the United States has already experienced 110% of the average full season tropical storm activity. In an average year, 33% of the seasonal average activity occurs by this date.

The CSU team's September-only forecast calls for five named storms, four hurricanes and two major hurricanes. Historically, September is normally the most active month for hurricane activity. The October-only forecast predicts three named storms, two hurricanes and one major hurricane, also well above average.

The forecasters noted that storm activity in August was really off the charts this year. August witnessed five named storms, two hurricanes and one intense hurricane, which is about 150% of average August storm activity, they said.

As of the first of September, 12 named storms, four hurricanes and three major hurricanes have developed in the Atlantic basin this season. The long-term (1950-2000) average for an entire season is 9.6 named storms, 5.9 hurricanes and 2.3 intense hurricanes per year.

"The very active season we have seen to this point is far from over," said Klotzbach. "We expect that by the time the 2005 hurricane season is over, we will witness seasonal tropical cyclone activity at near-record levels."

In the forecasters' updated Atlantic seasonal hurricane activity forecast, 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 220% of the long-term average.

"This high forecast continues due to a variety of highly 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 said he 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 conditions that did not favor major hurricane development or the tracking of these storms across the United States coastline. According to Gray, 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 forecasters noted that the last 10 years have witnessed 137 named storms, 77 hurricanes and 38 major hurricanes in the Atlantic basin. During that period -- including 2004 where 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 and the early part of this season make very clear, citizens living along the East and Gulf Coasts should continually be prepared for the possibility of landfalling hurricanes," said Gray.

Looking at the last decade, Gray and Klotzbach believe the United States is in a new, multi-decadal era for increased storm activity. The storm seasons spanning 1995-2004 comprised the most active 10 consecutive hurricane years on record, and the 2005 season has followed this active trend, they said.

"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 likely span the next two or three decades."

While 'global warming' appears to be the catch-all phrase these days for global changes, the Colorado State forecast team emphasized that it does not attribute changes in recent or projected Atlantic basin hurricane activity to human-induced global warming. They said they view these changes in hurricane activity as resulting from long-period natural climate alterations that historical and paleo-climate records show to have occurred many times in the past.

The duo said they will be issuing a seasonal update of their 2005 Atlantic basin hurricane activity forecast on Oct. 3.

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