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NOAA’s updated 2011 Atlantic Hurricane Season Outlook
calls for an 85% chance of an above-normal season, and a 15% chance of a near-normal season. There is no expectation for a below-normal season. Therefore, 2011 is expected to become the twelfth above-normal season since 1995. This updated outlook reflects a higher likelihood of an above-normal season compared to the pre-season outlook issued in May, which indicated a 65% chance of an above-normal season. See NOAA definitions of above-, near-, and below-normal seasons. The Atlantic hurricane region includes the North Atlantic Ocean, the Caribbean Sea, and the Gulf of Mexico. The higher confidence of an above-normal season is based on several factors. First, as predicted in May, conducive atmospheric and oceanic conditions are now in place over the tropical Atlantic Ocean and Caribbean Sea (called theMainDevelopmentRegion- MDR). Second, these conditions are expected to persist throughout the peak months (August-October) of the hurricane season in association with the tropical multi-decadal signal, which has contributed to the high activity era that began in 1995. Third sea-surface temperatures in the MDRare the third warmest on record, models predict a continuation of very warm SSTsthrough the hurricane season. Fourth, there is a possibility of La Niña re-developing. Historically, this combination of conditions produces an active Atlantic hurricane season. In addition, several dynamical model forecasts of the number and strength of tropical cyclones indicate that an above normal season is likely. The 2011 season is expected to be comparable to a number of active seasons since 1995. We estimate a 70% probability for each of the following ranges of activity during 2011:
10 seasons with similar climate conditions and uncertainties to those expected this year. These ranges do not represent the total possible ranges of activity seen in past similar years. The official NHC seasonal averages are 11 named storms, 6 hurricanes, and 2 major hurricanes. |
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