2005's Hurricane Season Was "Unprecedented"

Willie Drye
for National Geographic News

November 29, 2005

Meteorologists are describing the 2005 hurricane season with one word:
unprecedented.

"Absolutely, as far as we know, this was unprecedented," said Keith Blackwell, a researcher at the University of South Alabama's Coastal Weather Research Center in Mobile.

There's a long list of reasons why this hurricane season, which ends Wednesday, will be regarded as one for the ages:

• The 26 named storms that formed made it the most active season on record. The previous record of 21 storms was set in 1933.

• The 2005 season also produced new records for the most hurricanes (13) and the most "major" hurricanes (7), ranking as Category Three or higher on the Saffir-Simpson scale. The scale rates hurricanes from one to five according to wind speeds and potential for causing damage.

• Four major hurricanes made landfall in the U.S., a new record.

• Five storms formed in July, a new record for that month. One of those storms—Hurricane Dennis—was the most powerful July storm on record.

• Three hurricanes—Katrina, Rita, and Wilma—reached Category Five status on the Saffir-Simpson scale. That's also a new record.

• Hurricane Katrina, which made landfall in Louisiana on August 29, essentially destroyed New Orleans with a storm surge that flooded the city and made much of it uninhabitable. More than 1,300 people were killed by the hurricane, most of them in Louisiana, Mississippi, and Alabama.

• Hurricane Wilma in October became the strongest hurricane known to have formed in the Atlantic Basin, which includes the Atlantic Ocean, the Gulf of Mexico, and the Caribbean Sea.

• Hurricane Vince, which also formed in October, became the first known tropical storm to strike Spain and Portugal.

• The cost of damages caused by 2005's storms is still being tabulated, but it will dwarf all previous seasonal totals. The insured losses probably will total at least 75 billion U.S. dollars, according to experts. Researcher Phil Klotzbach of Colorado State University said the total tab could be as much as 200 billion U.S. dollars, a figure he says is "just mind-boggling."

• The 2005 season set a new record on the net tropical cyclone (NTC) scale. NTC is a measure that takes into account the number of storms that form in a season, the intensity of the storms, and how long they last. 2005's NTC index is 249, which easily surpasses the previous record of 230 set in 1950.

Stormy Season Ends

On the storm-battered U.S. Gulf Coast, which was raked by four intense hurricanes, jittery residents are relieved that the long, stormy summer has ended.

"We're certainly happy the season is over," said A.J. Holloway, mayor of Biloxi, Mississippi, which was devastated by Hurricane Katrina on August 29. "I hope we never see anything like this again."

The violent summer of 2005 also brought the debate about global warning's possible effects on hurricanes to public attention.

Some meteorologists say there is a direct link between the increased hurricane activity and the presence of so-called greenhouse gasses in the atmosphere, which is causing hotter summers and warmer winters.

Others, however, say the stormier summers are caused by a natural cycle of ocean currents that affects the salinity of the water. When the salt content is slightly higher—as it is now in the Atlantic—the water is warmer, and more hurricanes form.

The cycles are thought to last from 25 to 40 years.

"I believe global warming may be having some effect on hurricanes, but it's very small," said Blackwell, the Mobile, Alabama, meteorologist. "It's not responsible for the [increased] activity. This year would have happened anyway."

There have been earlier periods of active hurricane seasons that alternated with less-active ones. During the early 20th century, hurricane seasons were less active. But an active cycle began in the late 1920s and lasted until about 1969.

Another less active cycle lasted from 1970 to 1994. But the summer of 1995 saw a dramatic increase in the number of storms. That active cycle is still continuing and is expected to last at least another ten years, perhaps longer.

Although the hurricane season runs from June 1 to November 30, hurricanes sometimes form out of season.

"In the last few years, we've had a few December storms," Blackwell said. "It's not out of the question this year either."

On December 6, Klotzbach and other researchers at Colorado State will release their first prediction for the 2006 hurricane season.

"I would be surprised if 2006 is a very inactive season," Klotzbach said.

Willie Drye is the author of Storm of the Century: The Labor Day hurricane of 1935, published by National Geographic Books.

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