Nature`s tropical child, the hurricane, is about to embark on its annual path 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 preliminary 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. The loss of a crucial satellite doesn`t make it any easier on the hurricane hunters.
Even with computers, sophisticated radar nets, hurricane-hunting jets and satellites, making predictions about hurricanes still is an iffy business. But because more people keep moving to the water`s edge–41 million are on the Eastern U.S. coasts at last count–predicting the path of nature`s most destructive force is more essential than ever.
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 the 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 the 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.
Of the 41 million people living on the coast from Maine to Texas, 80 percent never have felt the direct hit of a hurricane.
”A false sense of security often prevails because of that,” Sheets said.
Preliminary predictions indicate this year`s hurricane season, which runs from June 1 to 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. Still under analysis were two other statistically significant factors–prevailing winds and atmospheric pressure in the Caribbean Basin.
Gray said he is sure about the absence of El Nino and the flow of stratospheric 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 along 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 would 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 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 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 of 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. Although the peak Atlantic season runs from June through November, most hurricanes occur in August, September and October.
Despite its massive power, a hurricane really is a delicate creature, requiring just the right temperatures, moisture, pressure and wind patterns to give it birth and keep it going.
That`s why there are only four areas in the world where hurricanes form and each area has its own brand name–baguio in the Philippines, cyclone in the Indian Ocean, typhoon in the Pacific and hurricane in our hemisphere.
Compared to the great cyclonic storm systems of the temperate zone, such as the ones that march across the midwestern United States, hurricanes are of moderate size and their intensity is dwarfed by the exploding force of a tornado. Yet their broad spiral base may dominate weather from the Earth`s surface into the lower stratosphere.
In an average year, about 100 ”seedling storms” will form over Africa or the Atlantic and move westward. Of these, 10 will intensify, be named and acquire gale-force 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. The one before that, Frederic in 1979, caused more damage than any other hurricane–$2.3 billion.
The worst storm in American history killed about 6,000 people in Galveston, Tex., in 1900. A Florida storm in 1928 blew a wall of water out of Lake Okeechobee and killed at least 1,800 people.
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.
In the last decade, the hurricane center has improved storm tracking and forecasting techniques to the point where at least 10 to 12 hours of daylight warning time can be guaranteed before a big storm slams into a populated area. Miami`s center is the central command post for a far-flung network of weather satellites, aircraft and a final ”picket line” of shore radar units stretched along America`s coast.
The National Weather Service has hundreds of meteorologists, but only five are hurricane specialists, an elite corps of weather experts who translate complex meteorology into concise weather bulletins.
But this year their job is more difficult. Forecasters lost a crucial satellite at the height of the 1984 season, meaning they must rely on one remaining watching satellite in a stationary orbit 22,300 miles above the coast of Brazil–where a satellite can monitor the tropics continuously.
In addition, there are satellites in much lower north-south orbits transmitting pictures of specific areas only twice a day.
”We`ll be operating this year with one satellite system, which means we cannot see out into the middle Atlantic as well as we could have,” Sheets said. ”We will fill in with other satellite data and extra reconnaissance flights.”
If the hurricane specialists lose their second satellite, an event that now appears unlikely, it would mean a return to the hurricane-hunting technology of the 1960s.
”If the second were to fail, we would have quite a problem,” Sheets said. ”We would be having to fill in with other types of data. We are preparing a back-up system just in case it does fail, but we`re not as nervous about it at this stage as we were last year.”
About two years ago the center launched a ”probability program,” which basically sets the odds for an area that may be hit by a hurricane.
”Instead of saying it may or could or might strike you, it tells you that the hurricane has a 1-in-5 chance of striking you within the next 24 hours,” Sheets said. ”It`s a very specific, hard number.”
Scientists still cannot predict the hurricane`s path more than a day in advance, whether it will stall in the ocean or turn toward land, fizzle out or surge in strength. Most importantly, scientists have not learned how to control the hurricane`s movement.
Science is supposed to be a business of hard facts, cold figures and dry statistics. But in the case of the hurricane, science has been known to fall flat on its face.
In 1965, Hurricane Betsy apparently was headed for a collision with the mid-Atlantic coast when it made an unusual about-face, roared south through the Upper Keys in Florida, where four people were killed, and then slammed into New Orleans, killing 58 more.
