An Uneasy Quiet Before The Storm

July 23, 1985|By Mark Schwed, United Press International

Nature's tropical child, the hurricane, has embarked on its annual season of unreliable, unpredictable, unstoppable frenzy.

This year we will know the greatest storms on Earth as Ana, Bob, Claudette, Danny, Elena, Fabian, Gloria, Henri, Isabel, Juan, Kate, Larry, Mindy, Nicholas, Odette, Peter, Rose, Sam, Teresa, Victor and Wanda.

If early predictions are on the mark, there could be some big trouble brewing in the Caribbean and Gulf of Mexico -- a return of the ferocious storms that have been noticeably absent for the last few years.

Even with computers, sophisticated radar nets, hurricane-hunting jets and satellites, making predictions about hurricanes still is an iffy business.

The decision to evacuate must be made at least a day and a half before a major hurricane makes a landfall, yet forecasters find it difficult to predict the path 24 hours ahead of a strike.

''It keeps getting worse,'' said Dr. Bob Sheets, acting deputy director of the National Hurricane Center in Miami.

Last year was the busiest season since 1981 with 12 named systems -- five hurricanes and seven tropical storms. The worst was Diana, which slammed into North Carolina coast in September, killed two people and caused $300 million in damage.

Yet Diana was the only hurricane to hit land and it was actually quite weak, a category 1-2 hurricane, by the time it hit a stretch of beach near Wilmington.

Preliminary predictions indicate this year's hurricane season, which lasts through Nov. 30, may be more violent than usual, with up to 15 storms that become hurricanes.

''The odds are for an above-average hurricane season,'' William Gray, a professor of meteorology at Colorado State University, said in Houston recently.

Gray cited two atmospheric conditions that statistically are linked to major storm seasons -- the absence of the El Nino phenomenon in the Pacific Ocean, and the lack of westerly winds above the equator.

El Nino, which occurs every two to seven years, is an unusual warming of eastern Pacific waters and can have far-reaching effects on global weather patterns, including the production of westerly winds that tend to block hurricanes from moving into the Gulf of Mexico or the East Coast.

In 1983, when there was a strong El Nino, only two hurricanes and two tropical storms developed, the least activity in 50 years.

The second phenomenon, high altitude winds, also favors hurricane development. They are flowing from the east, where the most violent hurricanes that afflict the Gulf Coast are formed -- off the western coast of Africa near the Cape Verde Islands.

Last year most of the hurricanes were middle latitude systems. There were no Gulf or Caribbean hurricanes, which historically are the strongest storms. ''If we return to a normal season, then we could expect more intense and even longer-lasting hurricanes than we had last year,'' Sheets said.

Hurricanes are the offspring of ocean and atmosphere. They are powered by heat from the sea, driven by the easterly trades and temperate westerlies, the high planetary winds and by their own fierce energy.

They are giant whirlwinds in which air moves in a large, tightening spiral around a center of extreme low pressure, reaching a maximum velocity in a circular band extending outward 20 or 30 miles from the rim of the eye. The circulation is counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.

Near the eye, hurricane winds may gust to more than 200 miles an hour, and the entire storm dominates the ocean surface and lower atmosphere over tens and thousands of square miles.

The hurricanes that strike the Eastern United States are born in the tropical and subtropical North Atlantic Ocean, the Caribbean Sea and the Gulf of Mexico. Most occur in August, September and October.

In an average year, about 100 ''seeding storms'' will form over Africa or the Atlantic and move westward. Of these, 10 will intensify, be named, and acquire galeforce winds. About six will become hurricanes and two will cross the coast of America somewhere with hurricane-force winds. About once in every three years a hurricane will cause a major disaster along the U.S. coast.

The last such ''supercane'' was Alicia, which mauled the most heavily populated corridor of Texas in 1981, killing six people and causing $2.1 billion in damage.

Most of the death and damage is brought by wind, flood-producing rains and, most lethal of all, the storm surge.

History is filled with storm surge catastrophes. In 1737, storm surges killed 300,000 people near Calcutta. In 1970, a cyclone's storm surge on the coast of East Pakistan killed 200,000 people, according to official estimates. Unofficial estimates were as high as 500,000.

Vastly improved warning and protection systems have systematically reduced the death toll from hurricanes.

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