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More major hurricanes predicted

BY P.J. HELLER | Fort Collins, CO | April 10, 2000

For residents living along the Atlantic and Gulf coasts, there's good news and bad news as this year's hurricane

season approaches.

The good news: Hurricane activity will be less active this year than the past four years. The bad news: There's an

increased likelihood of a major hurricane making landfall on the East Coast and Florida Peninsula and the potential

for more major storms in the years ahead.

Those are the latest predictions of forecaster William M. Gray, a Colorado State University (CSU) professor of

atmospheric science who issues hurricane predictions annually. Gray is predicting the June 1 to Nov. 30 storm

season will be "moderate" with 11 named storms, seven of which could reach hurricane strength with sustained

winds of 74 miles per hour. Three of those storms are expected to be intense hurricanes (Category 3, 4, or 5) with

winds of more than 110 mph, he said.

"We do not anticipate a season as active as those in 1995, 1996, 1998, or 1999," Gray said. "Still, we believe we are

entering a new era for increased storm activity and for East Coast landfalls by major storms. There is a strong

likelihood that in coming years we'll see more major storms as we did during the 1940s, 1950s, and 1960s."

Long-term averages based on the period 1950-1990 show 9.3 named storms, 5.8 hurricanes, and 2.2 intense

hurricanes per year. The 1999 hurricane season, which saw some of the most powerful storms ever, saw 12 named

storms, eight hurricanes and five major hurricanes with winds of up to 155 mph. Gray's updated April forecast was

similar to the predictions he issued in December. Further updates are due in June and August.

"As we see it now, things are progressing about as we thought they would in our early December forecast," he said.

"We do not believe that an El Nino will occur this year. However, the very cold (La Nina) water that's been out in

the eastern equatorial tropical Pacific for the last two years we think will modify somewhat and not be quite as cold.

That is a bit of an enhancing factor for this year's activity," he noted. Gray said there was an above-average chance

of a major storm hitting the East Coast and Florida Peninsula or the Caribbean Basin and an average probability of

a major hurricane slamming the Gulf Coast.

Specifically, he said chances of a major Category 3 storm (winds in excess of 110 mph) making landfall were 39

percent along the U.S. Atlantic coast (the average for the last century was 31 percent); 34 percent along the Gulf

Coast compared to a 30 percent average for the last century; and 60 percent along the entire U.S. coast, from

Brownsville, TX, to the Canadian border (long-term average is 52 percent). Chances of hurricane landfall in the

Caribbean Basin was 10 percent greater than the last century's average.

Gray said the increased likelihood of a major hurricane hitting the East Coast or Caribbean Basin was due to the sea

surface temperatures in the North Atlantic which he said continue to be relatively warm. Those conditions, he said,

indicate that the Atlantic Ocean thermohaline circulation system, or Atlantic conveyor belt, remains strong. Gray

and his colleagues said they believe that a strong Atlantic conveyor belt contributes to the formation of greater

numbers of intense Category 3,4, or 5 storms. That in turn increases the chances of major hurricane landfall on the

East Coast and in the Caribbean.

Gray also said he expected that hurricane formation would occur earlier this season compared to the 1998 and 1999

seasons. "Only one tropical storm, Arlene, had occurred during the first two months of the season last year, after

which, in late August, four hurricanes formed in quick succession," he said. Gray and his team of researchers said

one of the "climate factors" that could limit hurricane formation involved stratospheric, equatorial east-west winds.

Known as Quasi-Biennial Oscillation, the winds change direction from east to west and then west to east every 12 to

16 months. "This year, the Quasi-Biennial Oscillation is expected to blow from the east, a direction not normally

favorable to hurricane formation," Gray said. "However, this year the winds have failed to drop as low as we

expected, somewhat neutralizing their effect."

The CSU researchers base their predictions on a variety of climatic factors, including stratospheric winds, North

Atlantic sea surface temperatures, La Nina-El Nino conditions and west African rainfall. For the 1999 hurricane

season, Gray had predicted 14 named storms, nine hurricanes, and four major hurricanes. The season ended with 12

named storms, eight hurricanes, and five major hurricanes.


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