Colorado State Team Issues First Post-August Storm Season Update and September-Only Hurricane Forecast – Reduces Predictions

Note to Editors: Forecast totals are in the attached chart. The complete updated hurricane forecast, including the new September monthly forecast, a detailed description of forecast factors, press releases and additional information are available on the World Wide Web at or at

For the first time in more than 19 years of Atlantic basin hurricane forecasting, atmospheric scientist William Gray and the Colorado State University hurricane forecast team, including include Chris Landsea and Philip Klotzbach, are issuing an end-of-August seasonal update, a September-only hurricane forecast and a prediction for the remainder of the 2002 storm season. The new forecasts, based on meteorological information analyzed through August, call for a 2002 hurricane season that will be even less active than previously anticipated.

The updated forecast reduces the August 7 prediction of nine named storms, four hurricanes and one major hurricane to eight named storms, three hurricanes and one major hurricane (the long-term average is 9.6 named storms, 5.9 hurricanes and 2.3 major hurricanes per year). The team also foresees a significantly lower than average probability of United States and Caribbean basin hurricane landfall for the remainder of 2002. Gray warns, however, that people living along the southeastern U.S. coastline and in the Caribbean basin must remain alert and prepared.

"Information obtained through August indicates that the 2002 Atlantic basin seasonal hurricane activity will be much below average, and even slightly below what was predicted in early August," said Gray. "Due to the unusual and unexpected massive rearrangement of global ocean and atmospheric conditions the last three to four months, our forecasts have been revised downward to reflect recent inhibiting hurricane conditions and these cyclone suppressing influences are expected to persist for the remainder of the 2002 hurricane season."

These inhibiting conditions include below average sea surface temperatures, above average sea level pressure, above average strength of easterly trade winds, a strengthening El Niño event in the Pacific, and most importantly, stronger than average upper tropospheric westerly winds throughout the Atlantic tropics.

"Due to recent changes in climate signals, we believe the 2002 Atlantic basic hurricane season will be considerably below the long term average and much below what has been experienced in six of the last seven years."

A new aspect of the Colorado State team’s climate research is the development of hurricane activity predictions for individual months, including the first ever September-only Atlantic basin hurricane forecast. The individual monthly forecasts provide valuable information for shorter time periods and aid with the team’s seasonal predictions.

"There are often monthly periods within active and inactive hurricane seasons which do not conform to the overall season. The same factors that can make September an active or inactive storm month are often not the same factors that can make the entire season active or inactive," said Gray. "To this end, we have developed new techniques that use different parameters than the seasonal forecasts to predict storm activity within shorter time periods."

The new September-only forecast calls for three named storms, two hurricanes and one major hurricane. The predicted storm activity is only 54 percent of the long-term September average but will make up the majority of the remainder of this year’s storm activity. According to Gray, his team hopes to continue to improve its forecasts to provide people with specific monthly hurricane forecasts and specific landfall probability forecasts throughout future seasons.

As for the remainder of this year’s storm activity, Gray and his team predict an early end to the 2002 hurricane season, which officially lasts through the end of November, with the majority of the season’s activity occurring in September. The Colorado State team predicts that only one named storm, one hurricane and no major hurricanes will take place after September.

"During El Niño years, October and November hurricane activity is typically suppressed," said Gray. "Given that 2002 now has a moderate El Niño event, we expect October and November hurricane activity for this year to be below average."

William Gray and his Colorado State University team have provided seasonal hurricane forecasts for the last 19 years. The seasonal forecasts have traditionally been issued only in early December April, June and August. The forecasts are now beginning to include individual monthly predictions of Atlantic basin activity and seasonal and monthly U.S. hurricane landfall probabilities.

The storm seasons spanning 1995-2001 comprised the most active seven 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. This year is expected to be one of these temporary deviations from the long-period average.

The Colorado State forecast team does not attribute changes in recent and projected Atlantic hurricane activity to human-induced global warming or any other human-caused phenomenon. They believe the changes are a natural consequence of climate variability that has been a continuing feature of atmosphere-ocean changes since the last Ice Age.

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


Tropical Cyclone Parameters and 1950-2000 Climatology (in parentheses) May 31 2002 Forecast August 7 2002 Forecast Observed 2002 Activity Through August New September Only Forecast Forecast Activity After September September 2 2002 Revised Forecast
Named Storms (9.6)* 11 9 4 3 1 8
Named Storm Days (49.1) 55 35 7 13 6 25
Hurricanes (5.9) 6 4 0 2 1 3
Hurricane Days (24.5) 25 12 0 7 3 10
Intense Hurricanes (2.3) 2 1 0 1 0 1
Intense Hurricane Days (5.0) 5 2 0 2 0 2
Net Tropical Cyclone Activity (100%) 100 65 9 26 10 45

* Number in ( ) represents average year totals based on 1950-2000 data.