There is a 45% probability of a near-normal Atlantic hurricane season in 2002, a 35% probability of an above-normal season, and a 20% chance of a below-normal season, according to a consensus of scientists at the National Oceanic and Atmospheric Administration's (NOAA) Climate Prediction Center (CPC), the Hurricane Research Division (HRD), and the National Hurricane Center (NHC). This outlook represents the mixed combination of weak El Niño conditions and ongoing decadal-scale anomalies that are more conducive to an above-normal season.

The projected 2002 activity is centered approximately on the border between a near normal and an above-normal season, with a somewhat higher probability of being in the near-normal range. The 2002 season is not expected to be extremely active, as was observed during four of the last seven seasons (1995, 1996, 1998, 1999). However, it is expected to be more active than most of the relatively quiet 1971-1994 period.

DISCUSSION

1. Expected Level of Overall Activity - Near-normal to slightly above normal

Based on the current and expected climate conditions there is a 45% probability of a near-normal Atlantic hurricane season in 2002, a 35% probability of an above-normal season, and a 20% chance of a below-normal season. Using the "Accumulated Cyclone Energy" (ACE) index as the basis for measuring overall seasonal activity (see Background Information), the total 2002 activity is expected to range between 95%-135% of the long-term median ACE value (Fig. 1). This predicted range is centered slightly below the border (120% of median) between near normal and above normal activity, and emphasizes the higher probability of the near-normal range.

The historical record indicates a likely range of 9-13 tropical storms this season, which reflects larger uncertainty in the number of named storms when no significant El Nino or La Nina is present. The historical record also indicates that 85% of comparable seasons featured 6-8 hurricanes, and 70% featured 2-3 major hurricanes [categories 3-4-5 on the Saffir-Simpson scale].  Only 55% of these seasons yielded the combination of 9-13 tropical storms, 6-8 hurricanes and 2-3 major hurricanes.   Thus, while it is reasonable to expect the above range of tropical storms and hurricanes, the season can certainly feature near-to slightly above- normal levels of activity without all three of these criteria being met.

Based on past historical data similar seasons have also averaged 2 landfalling hurricanes in the continental United States and 1-2 hurricanes in the region around the Caribbean Sea.  However, it is important to recognize that it is currently not possible to confidently predict at these extended ranges the number of U.S. landfalling hurricanes, the intensity of the landfalling hurricanes, or whether a particular locality will be impacted by a hurricane this season.

2. Expected Climate Conditions- Weak El Nino-related impacts expected to be minimal

The ongoing multi-decadal signal that is conducive to increased hurricane activity, combined with a developing weak El Niño with minimal expected impacts, will likely result in overall levels of activity approximately bordering between a near-normal and above-normal season. The impacts from these climate conditions are expected to be approximately similar to those observed during the 2001 season.

For the past several hurricane seasons the favorable decadal signal has been evident in above-normal North Atlantic sea-surface temperatures, in an overall amplified West African monsoon system, in a favorable configuration of the African easterly jet, and most importantly in reduced vertical wind shear over the heart of the hurricane development region. Similar conditions contributed to the active decades of the 1950's and 1960's, and to the dramatic upturn in hurricane activity observed since 1995. See the recent paper by Goldenberg et al. (2001) in Science for more details.

A secondary climate factor, anomalously westerly winds in the lower stratosphere, is expected to provide a slightly enhancing influence on overall Atlantic hurricane activity this season.
Collectively, these climate conditions indicate a 45% chance of a near-normal hurricane season, a 35% chance of an above-normal season, and a 20% chance of a below-normal season.

3. Uncertainties in the Outlook

This outlook is based on the expectation of continued weak El Niño conditions, coupled with a modestly active multi-decadal signal, during the normal August-October peak in Atlantic hurricane activity. The main uncertainty for this outlook is the El Niño intensity during these three months. If the El Niño becomes stronger than expected it would likely increase the vertical wind shear in the heart of the hurricane development region and cause a decrease in overall activity.

We will closely monitor these evolving climate conditions prior to the release of an updated outlook in early August, which is the traditional beginning of the active portion of the Atlantic hurricane season.

CAUTIONARY NOTES

1) It is important to recognize that it is currently not possible to confidently predict at these extended ranges the number of U.S. landfalling hurricanes, the intensity of the landfalling hurricanes, or whether a particular locality will be impacted by a hurricane this season. Therefore, residents and government agencies coastal and near-coastal regions should always maintain hurricane preparedness efforts regardless of the overall seasonal outlook

2) Far more damage can be done by one major hurricane hitting a heavily populated area than by several hurricanes hitting sparsely populated areas or, of course, not making landfall at all.  Therefore, hurricane-spawned disasters can occur even in years with near-normal or below-normal levels of activity.  Examples of years with near-normal levels of activity that featured extensive hurricane damage and numerous fatalities include 1960 (Hurricane Donna), 1979 (Hurricanes David and Frederic), and 1985 (Hurricanes Elena, Gloria and Juan).  Moreover, the nation's most damaging hurricane, Andrew in 1992, occurred during a season with otherwise below normal overall activity.

FORECASTERS

Dr. Lixion Avila, Meteorologist, National Hurricane Center; ph: 305-229-4410; lixion@nhc.noaa.gov

Dr. Gerald Bell, Meteorologist, Climate Prediction Center; ph: 301-763-8000 x7536; gerry.bell@noaa.gov

Dr. Muthuvel Chelliah, Physical Scientist, Climate Prediction Center; ph: 301-763-8000 x 7546; muthuvel.chelliah@noaa.gov

Mr. Stanley Goldenberg, Meteorologist, Hurricane Research Division; ph: 305-361-4362; stanley.goldenberg@noaa.gov

Dr. Christopher Landsea, Meteorologist, Hurricane Research Division; ph: 305-361-4357; chris.landsea@noaa.gov

Dr. Richard Pasch, Meteorologist, National Hurricane Center; ph: 305-229-4411; richard@nhc.noaa.gov