William Gray and Colorado State Team Slightly Increase Seasonal Forecast: Call for Above Average Hurricane Activity in 2004

Note to Editors: The complete hurricane forecast, a detailed description of forecast factors, press releases and access to downloadable audio and video clips will be available by 8 a.m. MST April 2 on the Web at www.colostate.edu.

Colorado State University tropical storm researcher William Gray and his hurricane forecast team have slightly increased their seasonal predictions and call for above average Atlantic basin hurricane activity in 2004.     

"A wide variety of global predictors obtained and analyzed through March continue to point to the 2004 Atlantic basin hurricane season being an active one," said Gray. "We expect tropical cyclone activity to be about 145 percent of the average season."

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. Of these, 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. The team’s early December forecast called for 13 named storms, seven hurricanes and three intense hurricanes.

The Colorado State forecast team also warns of the considerably higher than average probability of at least one intense hurricane making landfall in the United States this year. According to today’s updated forecast, there is a 71 percent chance of a major 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 52 percent (long term average is 31 percent). For the Gulf Coast from the Florida Panhandle westward to Brownsville, the probability is 40 percent (the long-term average is 30 percent).The team also calls for above-average major hurricane landfall risk in the Caribbean.  

"The United States has been very lucky over the past few decades in witnessing very few major hurricanes making landfall in Florida and along the East Coast, but climatology will eventually right itself and we must expect a great increase in landfalling hurricanes," said Gray. "We don’t know when it will happen, but with the 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."

On a long term basis, intense hurricanes account for only about a quarter of all named storms, but cause about 85 percent of all tropical cyclone-spawned destruction.

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. Before Lili made landfall as a category 1 hurricane in October 2002, a record 21 consecutive Atlantic basin hurricanes did not cross the U.S. coastline.

The storm seasons spanning 1995-2003 comprised the most active nine hurricane years on record, and Gray thinks that 2004 will follow this active trend. The Colorado State forecasting team believes that the United States is in a new multi-decadal era for increased storm activity.

"We believe that the United States has entered a new era of enhanced major hurricane activity, reflective of the high activity during seven of the last nine years," said atmospheric research scientist and forecast team member Philip Klotzbach. "We expect this active tropical cyclone era to continue this year and to span the next two or three decades."  

Today’s report discusses how this new era correlates with a major reconfiguration of the distribution of the Atlantic thermohaline circulation that began in 1995. This change has warmed North Atlantic sea surface temperatures and lowered tropical Atlantic surface pressure, which in turn enhanced Atlantic basin hurricane activity. Despite the El-Nino-linked seasonal reductions in 1997 and 2002, the past nine years constitute the most active consecutive years on record for Atlantic basin tropical cyclone activity. The forecast team does not anticipate El Nino conditions in 2004.  

The Colorado State forecast team does not attribute changes in recent and projected Atlantic basin hurricane activity to human-induced global warming.  

Gray and his team are consistently working to improve their forecast methodologies based on a variety of climate-related global regional predictors.  For a detailed description of the forecast factors, visit the Web at http://typhoon.atmos.colostate.edu.

"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 Gray. "Our ongoing forecast research is allowing us to continually improve hurricane prediction skill."

Gray and his forecast team will issue seasonal updates of the 2004 Atlantic Basin hurricane activity on May 28, Aug. 6, Sep. 3 and Oct. 1. The August, September and October seasonal updates will also include the team’s new August-only, September-only and October-only storm activity.  

In addition to Gray and Klotzbach, other team members include William Thorson, Amie Hedstrom and others.