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NATURE

La Niña intensifies threat of hurricane season

La Niña
This image from NASA shows La Niña as a large blue swell in the Pacific Ocean  
VIDEO
Science Correspondent Ann Kellan reports on what the comeback of La Nina means for hurricane season
Windows Media 28K 80K

September 10, 1999
Web posted at: 10:28 p.m. EDT (0228 GMT)


In this story:

Affects jet stream

RELATED STORIES, SITES icon



By Science Correspondent Ann Kellan

(CNN) -- This hurricane season has been normal so far, with two hurricanes hitting land. But forecasters say brace yourself -- the second half of the season could be a replay of last year -- with devastating storms like Bonnie and Mitch.

Scientists say La Niña is to blame. That's the weather phenomenon characterized by cooler than normal waters in parts of the Pacific.

Early this spring, it looked like La Niña was fading. NASA's Tony Busalacchi says now it's making a comeback, with cooler Pacific waters stretching as much as 6,000 miles.

"There's still a reservoir of cold water at depth in the ocean, and when the winds in the equatorial Pacific strengthen as they normally do on seasonable time scales, it brought cold water up to the surface like we saw in the past month," Busalacchi said.

Affects jet stream

La Niña, like its counterpart El Niño, dramatically affects the jet stream -- the high winds that guide weather patterns in the United States.

When Pacific waters were warmer with El Niño, the sub- tropical jet stream shifted south, which worked to block and weaken hurricanes headed toward the Eastern United States.

La Nina, on the other hand, leaves the door open for the onslaught.

"Jet stream recedes, unfortunately it allows these hurricanes to spin up and quite often make landfall in the Eastern Seaboard of the United States," Busalacchi said.

There were seven hurricanes that hit landfall during the 1998 hurricane season. This year, so far, there have been two. Like last year, the second half of the season was when the most powerful storms hit shore.

So it's not over yet. Scientists say it could last another one to three months, taking us through the fall, which is the last half of hurricane season, and maybe early winter.



RELATED STORIES:
As hurricane season peaks, forecasters warily eye Floyd
September 10, 1999
El Niño calms Atlantic hurricane season
September 3, 1999
El Niño wasn't so bad after all, climatologist says
September 1, 1999
Scientists: El Niño may slow global warming
April 15, 1999
Meteorologist sees link between global, El Niño
February 23, 1999

RELATED SITES:
National Weather Service Home Page -U.S. Government warnings & forecasts
NOAA La Niña page
La Niña Summit
NOAA/PMEL/TAO El Niño & La Niña Predictions and Forecasts
TAO Temperature and Dynamic Height Animation
ENSO Visualizations
Meteorology Guide: the online guides
TROPICAL PREDICTION CENTER/NATIONAL HURRICANE CENTER
Hurricane and Storm Tracking
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