From: Reuters
Published May 20, 2008 05:45 PM

African dust forecast could be new hurricane tool

By Jim Loney

MIAMI (Reuters) - A new forecasting tool launched by a U.S. university on Tuesday will track clouds of African dust over the Atlantic Ocean as a possible indicator of the severity of a coming hurricane season.

The technique launched by researchers at the University of Wisconsin-Madison may help weather watchers, energy and commodities traders and anyone else riveted by hurricane predictions to gauge what might be coming in cyclone-prone areas of the Atlantic and Caribbean.

Dust storms originating in the Sahara Desert are believed to affect Atlantic hurricanes by blocking the amount of sunlight hitting the ocean. Hurricanes draw their energy from warm sea water.

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Amato Evan, a pioneer of research into the links between Saharan dust and hurricanes, said the first seasonal forecast calls for an average amount of dust and an average amount of ocean cooling -- about 1.8 degrees Fahrenheit (1 degree C) -- relative to the last 30 years for which data is available.

His forecast uses satellite measurements of the amount of sunlight reflected back into space to calculate dust levels over the area where hurricanes form.

"It gives us a sense of the total amount of dust over this one area of the tropical Atlantic," Evan said." "We think there is a strong link between dust and the formation of hurricanes and their intensification."

Evan's research has indicated that dust clouds, which can be as big as the continental United States and spread as far as the Caribbean and Central America, can cool the Atlantic from 1 to 2 degrees F (0.56-1.12 degrees C) during the summer.

Such a small difference can make a large difference in the number and intensity of hurricanes that form.

Interest in African dust rose after the disastrous 2004 and 2005 hurricane seasons, when dust levels were low.

Four powerful storms hit Florida in 2004, while 2005 shattered records with 28 storms, including Hurricane Katrina, which caused $80 billion in damage on the U.S. Gulf Coast.

"We expect to see a lot more dust this year than we saw in 2004 and 2005," Evan said. "On average that could lower the ocean temperature not even half a degree Celsius, maybe half a degree Fahrenheit. But that's a huge change in energy."

Researchers think the hot, dry clouds of dust may interfere with hurricanes by increasing wind shear, a change in wind speeds at different altitudes that can rip apart cyclones. They also inject dry air into the storms, which thrive on moisture.

Evan said he can predict African dust storm activity about eight months in advance.

Research into dust storms and their impact on cyclones is relatively new and hurricane forecasters have been reluctant to incorporate it into seasonal predictions. But Evan said leading researchers are increasingly looking at it.

The University of Wisconsin planned to issue a forecast in May, before the June 1 start of the six-month Atlantic season, and update it in the first week of June, July and August.

(Editing by Michael Christie and Alan Elsner)

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