As Gulf Coast residents begin to clean up and dry out their towns and cities, the damage caused by Hurricane Katrina has yet to be fully assessed.
Some have compared the devastation caused by Katrina to the destruction caused during the Boxing Day Tsunami, which swept through the Indian Ocean on Dec. 26, 2004, killing between 170,000 and 250,000 people.
"[Katrina] is our tsunami," said A.J. Holloway, Mayor of Biloxi, Mississippi, in an article from the Biloxi Sun Herald.
No matter how bad the effects of Katrina turn out to be, it is clear that it is but one part of what has become, and will continue to be, a record-breaking hurricane season, according to records kept by the National Oceanic and Atmospheric Administration (NOAA). By the end of the hurricane season, a total of up to 21 storms are forecast to have formed, according to an August 2nd forecast issued by NOAA. If the number of named stores ends up reaching 21, 2005 will be tied with 1933 as the most active Atlantic hurricane season on record.
Since the 2005 Atlantic hurricane season began on June 1st, 15 tropical storms and hurricanes have formed. Of these, eight made landfall; four have hit the United States. 11 of the storms have broken records for the earliest formation of a storm beginning with the letters D through K, plus M, N and O. So far, three hurricanes - Dennis, Emily, and Katrina - have had maximum sustained winds of at least 150 mph. Hurricane Emily currently holds the record as the strongest storm to form prior to August., reaching a top sustained wind of 155 mph on July 16. So far, the 2005 hurricane season has broken the record for most storms formed in July (five storms formed) and August (seven storms formed).
According to NOAA figures, the median number of named storms that form in any given year is 10. The average season will have six hurricanes, including an average of 2.6 major hurricanes. With a little more than half of the hurricane season already passed, there have been 15 named storms. Seven storms have been classified as hurricanes, four of which have been further classified as major hurricanes (Category 3 or higher).
Although some may consider the hyperactivity of this hurricane season to be some sort of meteorological fluke, historical weather trends suggest just the opposite.
"Hurricane extremes are not random," said Dr. Gerald Bell, lead seasonal hurricane forecaster for NOAA, during a lecture at the Marian Koshland Science Museum yesterday. "Active and inactive seasons result from a coherent set of atmospheric conditions - there are no random events."
According to Bell, hurricane activity goes through 20-30 year periods of activity and inactivity. We have been in a period of above-normal hurricane activity since 1995. Bell says that the current period of above-normal activity should continue for another 10-20 years.
As has been the case for nine of the last 11 hurricane seasons (in 1997 and 2002, El Ni¤o caused the hurricane seasons to have below-normal activity), the current season is considered above-normal. There are a number of factors that cause a season to have above-normal hurricane activity.
One of the key factors involved is a higher-than-normal air pressure aloft. Higher pressure aloft causes the winds over the Atlantic to become easterlies.
Another key factor is an appearance of weaker-than-normal trade winds. According to Bell, weaker trade winds allow hurricanes and tropical storms to move further west, increasing the chances for a successful landfall. A third factor is lower air pressure at the ocean surface.
One final, important factor is higher-than-normal sea surface temperatures in the Gulf of Mexico and the central Atlantic. "This year, the temperature of the water has been well above normal, by about two to three degrees Fahrenheit. That's comparable to the warmest waters in the historical record."
It is likely that these higher-than-normal sea surface temperatures contributed to the intense strength exhibited by Katrina during its trek through the Gulf of Mexico. In addition, says Bell, "there was nothing [in the Gulf] to inhibit Katrina's development."
The Atlantic hurricane season officially ends on November 30th. Bell says that while hurricane season forecasts have been highly accurate since first being used in 1998, "current computer models aren't particularly hopeful more than a week out. I can't give a prediction of what exactly will happen during the remainder of the season."
According to the U.S. Census Bureau, approximately 87 million people could be affected by a tropical storm or hurricane making landfall along the East or Gulf Coasts. Because more people live in vulnerable areas than ever before, says Bell, "hurricane preparedness is the most important thing one can do to minimize impacts if a tropical storm or hurricane strikes"
