William Gray and Colorado State University Forecast Team Predict Another Active Hurricane Season for 2004

Note to Editors: Forecast totals are in the attached chart. The complete hurricane forecast report, a detailed description of forecast factors and access to downloadable broadcast quality audio, downloadable print quality images and video clips are available on the Web at www.colostate.edu or at http://typhoon.atmos.colostate.edu.

Following an active 2003 hurricane season, William Gray and the Colorado State University hurricane forecast team predict Atlantic basin hurricane activity to be above average again in 2004.

For their first extended-range forecast for the 2004 hurricane season released today, Dec. 5, Gray and his colleagues anticipate that 13 named storms will form in the Atlantic basin between June 1 and Nov. 30. Of these, seven will become hurricanes and three are expected to develop into intense or major 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. 2003 witnessed 14 named storms, seven hurricanes and three intense hurricanes.

"Our analysis of current and projected global atmospheric and oceanic predictors through November indicates that the 2004 Atlantic basin hurricane season will be an active one," said Gray. "We expect tropical cyclone activity in 2004 to be about 125 percent of the average season."

Gray and his team also estimate the probability of at least one major hurricane making landfall in the United States in 2004 to be about 30 percent above the long-term average. According to today’s report, there is a 68 percent chance of a major hurricane hitting somewhere along the U.S. coastline in 2004 (the long-term average probability is 52 percent). For the U.S. East Coast, including the Florida Peninsula, the probability of an intense hurricane making landfall is 48 percent (the long-term average is 31 percent). For the Gulf Coast, from the Florida Panhandle west to Brownsville, the probability is 38 percent (the long-term average is 30 percent).

The report also addresses the downturn in United States major hurricane landfall since 1995 despite the large increase in Atlantic basin major hurricane frequency during this same period. The nine years of 1995-2003 witnessed 32 major hurricanes forming in the Atlantic. Throughout the last century, an average of about one in three major Atlantic basin hurricanes made landfall. Based on this century-long average, nine or 10 intense hurricanes should have made landfall in the United States within the last nine years, but only three crossed the shoreline.

According to Gray, the United States has been extremely lucky over the past nine years, and the East Coast has been especially fortunate to have experienced only one major hurricane landfall (Fran in 1996) since 1995. During the active hurricane period of 1944-1961, there were 16 major landfall events along the East Coast.

"This good fortune during recent years was due in large part to a persistent upper-air trough located along the U.S. East Coast and a weaker-than-normal Bermuda high pressure in the west Atlantic. These conditions have caused a large portion of the northwest-moving major hurricanes to curve to the north before they reached the coastline," said Gray. "However, this good luck cannot be presumed to continue. Climatology will eventually right itself and we must expect a great increase in landfalling major hurricanes and hurricane-spawned destruction in coming decades on a scale many times greater than what we have seen in the past."

Major hurricanes account for only about a quarter of all named storms but cause about 85 percent of all tropical cyclone-spawned destruction.

Today’s report also discusses the 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, a trend well associated with the large increase in major hurricane activity throughout seven of the last nine years. 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.

"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 span the next two or three decades."

In this new era as in the past, there will be individual years with below-average numbers of hurricanes. The 1997 and 2002 seasons, for example, were two of those temporary deviations from the long-period average.

For the Dec. 5 forecast, Gray and his research team are using a recently developed six-to-11 month statistical forecast system based on 52 years of past storm season data. The new system, which provides strong statistical relationships for climate data, is improving 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 global and regional atmospheric and oceanic predictors previously shown to be related to forthcoming seasonal Atlantic tropical cyclone activity and landfall probability," said Klotzbach, who led the development of the new forecast scheme. "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 2004 hurricane season."

Gray, in his 21st year of forecasting Atlantic basin hurricanes, believes these and other recent improvements in the gathering, archival and data analysis techniques of global atmospheric and oceanic signals can be used to consistently improve forecasts of Atlantic basin hurricane activity and landfall probabilities.

"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."

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

Gray and his forecast team will issue seasonal updates of the 2004 Atlantic basic hurricane activity forecast on April 2, May 28 (to coincide with the official start of the 2004 hurricane season on June 1), 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 forecasts.  

In addition to Gray and Klotzbach, other team members include William Thorson, Jason Connor and others.




-Released Dec. 5, 2003-

Tropical Cyclone Parameters                 Extended Range

(1950-2000 Climatology Averages           Forecast for 2003

in parentheses)                

Named Storms (9.6)*                         13

Named Storm Days (49.1)                            55

Hurricanes (5.9)                          7

Hurricane Days (24.5)                         30

Intense Hurricanes (2.3)                         3

Intense Hurricane Days (5.0)                     6

Hurricane Destruction                          85

Potential (72.7)

Net Tropical Cyclone                          125

Activity (100%)

* Numbers in ( ) represent average year totals based on 1950-2000 data.

Note to Editors: The National Oceanographic and Atmospheric Administration (NOAA) also has begun to issue Atlantic basin seasonal hurricane forecasts. The NOAA forecasts are independent of the Colorado State University forecasts although they utilize prior Colorado State research which NOAA augments by their own insights. The public should not expect the NOAA and Colorado State forecasts to necessarily be in agreement.  NOAA makes its forecasts for a range of numbers and does not issue individual month or landfall probability forecasts.