William Gray and Colorado State Forecast Team Issue April Update: Maintain Predictions for Above-Average Hurricane Activity in 2003

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

Now in his 20th year of hurricane forecasting, Colorado State University tropical storm researcher William Gray and his research team maintain their prediction for well above average Atlantic basin hurricane activity in 2003. In the first seasonal update report of 2003, issued today (April 4), the team calls for twice as many hurricanes as in 2002.

"A wide variety of global indicators obtained and analyzed through March continue to point to 2003 being an active Atlantic hurricane season," said Gray. "We expect Atlantic basin tropical cyclone activity to be about 140 percent of average this year."

As detailed in today’s update, Gray and his colleagues maintain their exact extended-range forecast issued in early December and call for 12 named tropical storms to form in the Atlantic basin between June 1 and Nov. 30. 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 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.

Gray and his team believe that the El Nino in the Pacific, which played a role in suppressing 2002 hurricane activity, is weakening and will be largely dissipated by summer. Additionally, the Colorado State forecasters cite very warm sea surface temperatures combined with decreasing sea surface pressures in the north and tropical Atlantic as other factors that will make 2003 an above-active hurricane season.

Gray and his team also maintain their warning for higher than average probability of at least one intense hurricane making landfall in the United States in 2003. According to today’s updated forecast, there is a 68 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 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 team also expects above-average major hurricane landfall risk in the Caribbean.

"The United States has been extremely lucky over the past few decades, 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"

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 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 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 did not make shore along the U.S. coast.

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. 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 a temporary deviations from the long-period average, but 2003 is expected to be in line with this new era.

"A remarkable upturn in Atlantic Basin hurricane activity has occurred the past eight years," Gray said. "We believe we have entered a new, multi-decadal era for increased storm activity, particularly an increase in the number of major hurricanes, which will likely last another two or three decades. Hurricane activity in 2003 is likely to reflect this more active era."

Gray and his team are consistently working to improve their forecast methodologies based on a variety of climate-related global and regional predictors. For the April 4 forecast, the team is using a new statistical scheme that focuses on an analysis of three diverse methodologies: one based on 45 years of past data, one based on 52 years of different data and a separate study of analog years which have similar precursor indicators to this year. Qualitative adjustments are then added to accommodate additional processes which may not be represented by the two statistical analyses. The new strategy is expected to further improve the team’s strong record of forecast accuracy. For a detailed description of the forecast factors, visit the Web at http://typhoon.atmos.colostate.edu/forecasts.

"Overall, we are making good progress with regard to 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 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, team members include Christopher Landsea, Philip Klotzbach, Eric Blake, William Thorson, Jason Conner and others.


Tropical Cyclone Parameters and 1950-2000 Climatology (in parentheses) Extended Range Forecast for 2003 April 4, 2003 Update
Named Storms (9.6)* 12 12
Named Storm Days (49.1) 65 65
Hurricanes (5.9) 8 8
Hurricane Days (24.5) 35 35
Intense Hurricanes (2.3) 3 3
Intense Hurricane Days (5.0) 8 8
Hurricane Destruction Potential (72.7) 100 100
Net Tropical Cyclone Activity (100%) 140 140

*Number in ( ) represents 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 use 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.