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HOME > Expert Assessments > Atlantic Hurricane Outlook
NOAA: 2001 Atlantic Hurricane Outlook

Issued: 9 August 2001

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Accompanying NOAA Press Release
May 2001 Hurricane Outlook August 2000 Hurricane Outlook
Atlantic Hurricane Outlook Archive

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) indicates an equal 40% probability of either an above-normal or near-normal 2001 Atlantic hurricane season, and a 20% chance of a below-normal season. This prediction calls for slightly more hurricane activity than was called for in the pre-season NOAA Outlook issued in May. The current outlook represents the mixed combination of ENSO-neutral conditions and ongoing decadal-scale anomalies that are more conducive to an above-normal season.

The 2001 hurricane season is expected to feature normal to slightly above-normal levels of activity. On average, similar seasons have featured 2-3 landfalling hurricanes in the continental United States, and 1-2 landfalling hurricanes in the region around the Caribbean Sea. The 2001 season is not expected to be hyper-active, as was observed during four of the last six seasons (1995, 1996, 1998, 1999). However, it is expected to be more active than most of the relatively quiet 1970-1994 period.


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

Given the current atmospheric and oceanic conditions (see also section 2 below) we expect a 40% chance of an above-normal hurricane season, a 40% chance of a near-normal season, and a 20% chance of a below-normal season. These probabilities have changed from the May Outlook, which indicated a 50% chance of a near-normal season, and a 25% chance of either an above-normal or below-normal season. Based on the “Accumulate Cyclone Energy” [ACE] index, which measures overall seasonal activity (see Background Information), we expect the total 2001 seasonal activity to fall between 100% -140% of the long-term median value. This range is higher than the 76% - 120% of median called for in the May outlook.

The historical record indicates that 58% of comparable seasons featured 9-12 tropical storms, 67% featured 6-8 hurricanes, and 67% featured 2-4 major hurricanes [categories 3-4-5 on the Saffir-Simpson scale]. Only 47% of the comparable seasons featured the combination of 9-12 tropical storms, 6-8 hurricanes and 2-4 major hurricanes. Thus, while it is reasonable to expect 9-12 tropical storms, 6-8 hurricanes and 2-4 major hurricanes this season, the season can certainly feature slightly above-normal levels of activity without all three of these criteria being met.

Based on past historical data similar seasons have averaged 2-3 landfalling hurricanes in the continental United States and 1-2 hurricanes in the region around the Caribbean Sea.

2. Expected Climate Conditions- Decadal-scale global climate patterns expected to dominate portions of the tropical North Atlantic: La Niña/ El Niño not expected to play important role

The prominent climate signals guiding the August Outlook are the expected continuation of ENSO-neutral conditions and ongoing decadal anomalies. During the peak (August-October) months of the hurricane season the regional decadal anomalies feature reduced vertical wind shear and above-average SSTs over key portions of the main development region, and increased cyclonic vorticity along the equatorward flank of the African Easterly Jet. All of these conditions are now in place, and all favor above-average hurricane activity by contributing to enhanced African easterly wave development. Similar anomalies contributed to the active decades of the 1950's and 1960's, and to the strong upturn in hurricane activity since 1995.

These regional anomalies are associated with global decadal patterns of enhanced tropical rainfall, and warmer-than-average sea-surface temperatures (SST) over the tropical North Atlantic in association with the Atlantic multi-decadal mode (Goldenberg et al. 2001; Science).

The above regional anomalies have strengthened considerably since mid-May and have become more conducive to hurricane formation and intensification, thus suggesting a higher probability of an above-normal season than was indicated in the May NOAA Atlantic Hurricane Outlook. Conversely, the persistence of ENSO-neutral conditions since mid-May, and the correspondingly lower probability that an El Niño episode will develop and adversely affect 2001 hurricane activity, suggests a reduced likelihood of a below-normal season compared to that indicated in the May outlook.

A secondary climate factor, easterly winds in the lower stratosphere, is also expected to provide a slightly suppressing influence on overall Atlantic hurricane activity this season.

Based on the historical record, this combination of climate conditions indicates a 40% chance of above-normal activity for the 2001 hurricane season, a 40% chance of normal activity, and a 20% chance of below-normal activity.


1) This Outlook represents our best estimate for the expected overall level of activity for the Atlantic basin.  No outlook can give certainty as to whether or not a particular locality will be impacted by a hurricane in any given year. Residents and government agencies of coastal or near-coastal regions should always maintain hurricane preparedness efforts, regardless of the overall outlook for a given year.

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. Because of this, hurricane-spawned disasters can occur even in years with normal (or below-normal) levels of activity. Examples of years with just 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 below-normal levels of activity.


This outlook is not designed to compete with hurricane outlooks issued by groups outside NOAA. We gratefully acknowledge the pioneering research of Dr. William Gray and others, which have significantly increased scientific understanding of the links between various climate factors (particularly the El Niño/ La Niña cycle) and the atmospheric circulation features that affect Atlantic hurricane activity. We also acknowledge the leading role that Dr. Gray and colleagues at the Colorado State University have played in developing and providing seasonal forecasts of Atlantic basin hurricane activity.


Dr. Lixion Avila, Meteorologist, National Hurricane Center; ph: 305-229-4410;

Dr. Gerald Bell, Meteorologist, Climate Prediction Center; ph: 301-763-8000 x7536;

Dr. Muthuvel Chelliah, Physical Scientist, Climate Prediction Center; ph: 301-763-8000 x 7546;

Mr. Stanley Goldenberg, Meteorologist, Hurricane Research Division; ph: 305-361-4362;

Dr. Christopher Landsea, Meteorologist, Hurricane Research Division; ph: 305-361-4357;

Dr. Richard Pasch, Meteorologist, National Hurricane Center; ph: 305-229-4411;

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Page last modified: August 9, 2001
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