For educational purposes only

http://www.cnn.com/2000/NATURE/11/30/hurricane/index.html

Earth in quiet period for hurricanes, researchers say Despite high-profile storms like Hurricane Keith in 2000, scientists say we have been in a relatively calm hurricane period for centuries November 30, 2000 Web posted at: 4:02 PM EST (2102 GMT)

(CNN) -- The active 2000 hurricane season that ended Thursday might suggest that the storm onslaught can't get much worse. But the Earth is actually in a 10-century-long quiet period for hurricanes, according to researchers.

New research shows that hurricane activity runs in cycles spanning thousands of years. And while at least 113 major hurricanes hit the U.S. Gulf and Atlantic Coasts during the last 50 years, the 20th century is at the tail end of a 1,000-year quiet cycle.

"In the last 1,000 years, the hurricane activities have died down again," said Professor Kam-Biu Liu, of Louisiana State University. "There were relatively few intense or catastrophic hurricane strikes along the Gulf Coast."

MESSAGE BOARD Environmental issues But this year's hurricane season continued a three-year trend of above-average storm activity. Fourteen named storms hovered over the Atlantic Ocean, Gulf of Mexico and Caribbean Sea, eight becoming hurricanes and three reaching major hurricane strength. Despite this, no hurricanes directly hit the United States this year.

"The main reason is that with the bulk of the hurricanes, we had an upper-level trough in the eastern United States, which helped steer them up to the north," said Max Mayfield, director of the NOAA National Hurricane Center. "The trough also provided unfavorable conditions aloft, which weakens the storms."

While Mayfield says he is familiar with studies in hurricane activity cycles, he points out that "we've had more tropical storms and hurricanes in the last six-year period than we've ever had."

"I try not to get too caught up in forecasting. You can only do so much with statistics. What really counts is where they hit and how strong they are at landfall," Mayfield said.

LSU researchers take sediment core samples from coastal lakes and marshes to learn about past storm seasons By taking core samples from the sediment at the bottom of coastal lakes and marshes, researchers can determine storm cycles. Fine-grained, dark sediment indicates a period when the waters were calm and there were no hurricanes. But an active storm season, such as a catastrophic hurricane strike, will wash sand from the shore into the lake, creating coarser-grained sediment.

After counting sand layers and determining their dates through carbon dating, researchers can develop a timeline of catastrophic hurricane strikes and quieter seasons. They can use this science, called paleotempestology ("paleo" means ancient, while "tempest" means storm), to predict the future by studying the past.

The Atlantic hurricane season begins June 1 and ends November 30. The NOAA Hurricane Center will not release predictions for the next hurricane season until next spring, but Liu had some long-term predictions.

"What we know is that the climate system is capable of producing a lot more catastrophic hurricanes that come our way. And so it is quite possible that this will happen again in the future," Liu said.

-- K. (infosurf@yahoo.com), December 01, 2000