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Forecasters Expect So-So Hurricane Season

Possible respite after three active years

TUESDAY, May 29, 2001 (HealthDayNews) -- If national weather forecasters are right, the East Coast finally may get a breather from a three-year bumper crop of hurricanes.

Although tornado predictions are harder to make, the summer also looks bright in the Midwest, where the number of twisters has been way below average so far this year.

The 2001 hurricane season, which officially begins June 1 and ends Nov. 30, is expected to be about average, meaning the Atlantic Ocean may spawn about 10 serious storms, including five or six hurricanes.

In an average season, no more than two hurricanes hit land in the United States.

"We don't see any distinguishing characteristics about this season that would make it stand out as a particularly strong or weak one," says Vernon Kousky, a hurricane expert at the Climate Prediction Center, part of the National Centers for Environmental Prediction. "But that doesn't tell us where they're going to form or where they're going to strike on land. We have no way of anticipating how many will hit the United States."

Luckily for those who live in hurricane country, a weather phenomenon known as La Niña is not active in the Pacific Ocean. "It has pretty much died now," Kousky says.

La Niña -- the opposite of the El Niño phenomenon -- cools waters in the Pacific Ocean. When La Niña is active, the atmosphere over the Atlantic becomes more friendly to hurricanes, because the winds high above the ocean are more likely to blow in the same direction as lower winds, Kousky says.

When winds blow in opposite directions at different levels, the tops of columns of thunderstorms are sheared off. "That's bad for hurricane formation," Kousky says.

In the last two years, La Niña has turned the Atlantic into a bustling hurricane factory. In 2000, for example, there were 14 large storms, including eight hurricanes; 1999 had 12 big storms, including eight hurricanes.

Kousky says the science of hurricane forecasting is improving, and meteorologists are much better at predicting where a hurricane will hit land. "We've made a lot of strides in the past five years."

Kousky says, "Emergency managers need to know what a likelihood of a more active or less active season is so they can distribute their resources. If you're a homeowner in one of these areas, and you know there's a greater-than-average likelihood of hurricane activity, it might make you spend more money to put a roof on or new shingles. There are things people can do if they're given a heads-up."

Tornado prediction is not nearly as advanced. While meteorologists can give three-day forecasts of conditions that may spawn tornadoes, they can give only about 10 minutes' warning before a tornado actually forms, says Daniel McCarthy, a meteorologist with the National Oceanic and Atmospheric Administration (NOAA) Storm Prediction Center.

Scienctists may take 15 years to develop finely tuned radar that will "sweep" the skies every minute, instead of every 6-12 minutes that's possible now, he says.

The prime time for twisters in the Midwest is from March 1 to July 1, particularly for "Tornado Alley," a region stretching from northern Texas to South Dakota.

So far this year, 300 tornadoes have struck. A typical tornado season spawns about 1,000 tornadoes.

Twisters tend to form when warm moisture from the Gulf of Mexico heads north and meets cold, wind-filled storms traveling east from the Rocky Mountains, McCarthy says. The wind and rain combine to form powerful thunderstorms, which can spin off tornadoes.

So far this year, the warm moisture has stayed to the south, creating conditions that aren't good for tornadoes, he says.

But that could change. If you can predict one thing about the weather, it's that no conditions are forever, McCarthy says.

What To Do

Learn more about how to prepare for hurricanes in this fact sheet prepared by the NOAA.

Get ready for tornadoes by reading this fact sheet by the Federal Emergency Management Agency.

Also, read previous HealthDay articles on the weather.

SOURCES: Interviews with Vernon Kousky, Ph.D., chief, analysis branch, Climate Prediction Center, National Centers for Environmental Prediction, Camp Springs, Md., and Daniel McCarthy, meteorologist, NOAA Storm Prediction Center, Norman, Okla.
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