Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.
By: Dr. Jeff Masters ,
Atlantic Hurricane season officially begins today, Wednesday, June 1, and runs through November 30. This year's season is expected to continue the trend of above-normal activity seen since 1995. Both NOAA and Colorado State Professor Bill Gray's team predict a much more active than usual season. NOAA expects a 70% chance of an above-normal hurricane season, a 20% chance of a near-normal season, and only a 10% chance of a below-normal season. Long-term averages for the number of named storms and hurricanes are 10 and 6, respectively. Bill Gray's team predicts 15 named storms and 8 hurricanes, with a 77% chance of at least one major hurricane (Category 3 or higher) hitting the U.S.
Among the factors expected to cause a more active hurricane season are:
1) The absence of El Niņo. According to NOAA's Climate Prediction Center, last year's weak El Niņo conditions ended in April 2005, and El Niņo conditions are not expected to recur during this year's hurricane season. There is a well-known link between El Niņo and Atlantic hurricane activity, with El Niņo favoring fewer hurricanes and La Niņa favoring more hurricanes.
2) Much warmer than average sea surface temperatures (SSTs). Atlantic SSTs are at their highest in over 50 years, and are close to being the highest on record. This means plenty of high-octane "fuel" for hurricanes.
3) We are in the middle of a multi-decadal period of high Atlantic hurricane activity. Atlantic hurricane seasons have decades-long periods of generally above-normal or below-normal activity. These fluctuations are tied to a complicated set of natural cycles that occur in the winds and ocean currents over the Atlantic. Beginning with 1995 all of the Atlantic hurricane seasons have been above normal, with the exception of two El Niņo years (1997 and 2002). This contrasts sharply with the generally below-normal activity observed during the previous 25-year period 1970-1994.
If you live in Florida, it's going to be tough to match last year's hurricane season, though. I compute the odds of at least four hurricances hitting Florida (3 of them major hurricanes) as happened in 2004 as a once in 300 year event. Two years back-to-back like that would happen once every 90,000 years.
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