On a hot, sultry day in mid-August, 1969, heavy with the strange calm that precedes a storm, thirteen airplanes sat on the alert at Roosevelt Roads, Puerto Rico, awaiting the order to take off and meet an enemy. The foe was a tropical cyclone -the storm called hurricane in the Caribbean, typhoon in the western Pacific.

Of all nature's furies, this is the most massive. With winds that sometimes reach more than two hundred miles an hour as they whirl around a circle that may be three hundred miles across, accompanied by thunder and lightning and unbelieva bly heavy rains, hurricanes are the deadliest and most destruc tive of storms. On any list of natural disasters, hurricanes are seldom far from the top. In the Bay of Bengal in November, 1971, a hur ricane destroyed nearly all life on thirteen islands, killing per haps one million people.

In the United States, hurricanes from the Caribbean and the Gulf of Mexico cause $300 million worth of damage every year on the average, to say nothing of the death, injury, a suffering they bring.

Single hurricanes, such as Betsy in the autumn of 1965, have caused more than $1 billion in destruction. The worst losses suffered by the United States Navy in World War II were not inflicted by the enemy, but by hurricanes in the western Pacific.

The hurricane problem is growing. Hurricanes are striking sooner in the year, hitting oftener, and ranging farther inland. The hurricane season used to start in mid-summer and confine itself mostly to the Gulf Coast. Now the storms are beginning as early as May. In 1955 there was even a hurricane that blew up out of the Lesser Antilles in January. Not since Columbus logged a hurricane in that vicinity in 1493 had one be known that early in the season.

And hurricanes are roaring up the Atlantic seaboard all the way to New England. With more and more people living those areas, the death and ruin each time adds up to a national calamity.

So when silver iodide first was proving to be an effective instrument to wring more rain from the clouds, the thought was not long in following that silver iodide might also in some way be used to moderate hurricanes. A harsh reminder of the need had just been provided by Hurricane Diane. Striking North Carolina on August 17, 1955, Diane rampaged up the coast, bringing southern New England the worst siege of wind and flood in its history. One hundred and eighty-four persons died. Damage estimates ran as high as $5 billion.

Dr. Robert H. Simpson, director of the National Hurricane Research Laboratories at Miami, Florida, believed that if freezing nuclei could be introduced into the clouds that sur round a hurricane, changing the moisture into ice crystals, this might unbalance the forces driving the storm and slow it up.

That a hurricane could be affected by seeding was apparent from what happened the first time it was tried, October 13, 1947, when a Navy plane released dry ice into one. The storm, which had been heading northwest out to sea, suddenly turned inland, striking Savannah, Georgia.

Dr. lrving Langmuir, who headed this seeding project for General Electric, believed the hurricane's change of course was caused by the seeding. Other scientists disagreed, but no one could be sure.

Many years later, Pierre St. Amand and his associates at the Navy Weapons Center at China Lake in the California desert announced that they had developed new seeding gen erators which made it possible to inject large amounts of silver iodide into a storm from an airplane in moments. The seeder thus could do his work fast and retreat to safety.

Flying airplanes fitted with the new generators, groups from the Navy and the Weather Bureau cautiously tried out Dr. Simpson's theory on Hurricane Esther in September, 1961. They dipped gingerly into the storm and gave it a seeding on each of two days. The winds slowed, but was it because of the seeding? Would the winds have slowed anyway?

To try again-and keep trying-Project Stormfury was set up as a joint effort of the Navy and the Environmental Science Administration of the Department of Commerce, with Dr. Simpson as director. The scientists settled down to wait for the next suitable hurricane.

Not every hurricane qualifies for experimental tampering as the lesson of 1947 taught. These incredibly powerful storms are highly unstable and erratic, Dr. Simpson cautioned. They slow down, speed up, and change course. Therefore, those selected for seeding must be well out to sea, with no more than a ten percent chance of reaching land in the next twenty-four hours, whatever happens.

Landing of the hurricane could confuse the results of the seeding, spoiling the experiment. Also, the seeders might be blamed for the landing, exposing them to lawsuits.

Hurricane Beulah, arriving after a two-year wait, met the requirements. Like Esther, Beulah was given a heavy dose of silver iodide two days in a row. Again, there was an encourag ing slowing of the winds, as with the seeding of Esther. But the question still remained: Was it the silver iodide that cause it?

Once more, results were encouraging but not conclusive

Six years passed before the chance came to try again. The new target was Hurricane Debbie, which brings us back to those airplanes waiting on the ramp at Puerto Rico that August day in 1969.

There was a double incentive to go out and intercept the oncoming Debbie. As she gathered her forces east of Puerto Rico, Hurricane Camille was howling ashore in Mississippi. There had never been a hurricane like Camille as far as anyone knew. Some hurricanes had done more harm, but for sheer ferocity Camille beat them all.

It drove barometers nearly out of sight. Spinning at more than two hundred miles an hour, the highest hurricane speed ever recorded, Camille spawned a family of more than one hundred tornadoes and dragged a thirty-foot tidal wave ashore in her wake. Between the wind and the water whole towns were wiped out between Gulfport and Biloxi, sending more than 200,000 people fleeing for their lives. There were floods as far north as Virginia.

When finally it ended, 132 people were dead and the de struction stood at $1 billion.

Fortunately the alarm had gone out in good time, thanks to the eyes of a satellite high above which had been tracking the hurricane since it began as an ordinary rain storm off the coast of Africa. If it had not been for the watchdog in space, Ca- mille might have outdone the hurricane that hit Galveston, Texas, in 1900, rolling a tidal wave over the city which drowned 6,000 people.

Hurricane Camille, Dr. Simpson said, "was the greatest storm of any kind that has ever affected this nation." The hurricane hunters waiting for Debbie while Camille wrought devastations were wiser than they had been in the first experiment, with Hurricane Beulah. During the long wait they had done their homework, boning up on the nature and habits of hurricanes.

In addition, under the leadership of Joanne Simpson, dir rector of the Experimental Meteorology Laboratory at Coral Gables, Florida, and professor of Atmospheric Science at the University of Miami, improved silver iodide generators had been developed. These were now in place on the planes. So the time had been well spent.

As Debbie finally passed within range, fully mature, with winds doing better than 115 miles an hour, the hunters took off. Coming alongside the great, dark mass of swirling clouds the five Navy planes plunged inside and crossed the eye, loos ing silver iodide as they went. In two or three minutes they came out.

Two hours later, the seeders struck again. Five times that day, August 18, they dived into the hurricane with large doses of silver iodide, waiting two hours between flights.

Meanwhile, as each seeding foray was made, two accom panying monitor planes took turns crisscrossing the storm from one side to the other, to see what was happening, measur ing temperatures, pressures, cloud contents, and wind speeds.

A great deal was happening. The winds were slowing sharply. They started falling soon after the second seeding, and they kept on falling until five or six hours after the final seeding. By then, the winds were down from a high of 115 miles an hour to 78, somewhat stronger than a gale.

In another two days the seeders repeated the experiment. Once more the winds, which had speeded up again during first night, began to slow as the seeding progressed. Six hours after the last assault with silver iodide, the winds were down from about the same high as on the first day, or 115 miles an hour, to 98. In fifty other hurricanes studied, but not seeded, there had been no such change in the winds.

"A huge operational success," said Dr. R. Cecil Gentry, head of Stormfury. who personally took part in the experi ments, the first multiple seedings of a hurricane ever made. They did what they set out to do, Dr. Gentry said. They put the silver iodide where they planned to put it, and they got the kind of information they were after.

"The evidence offers some hope that it may be possible to reduce hurricane intensity by means of silver iodide seeding," the National Academy of Sciences says carefully. But, it added, there needs to be more research before the question can be settled for sure.

"Additional seeding tests should be conducted as soon as possible," it urged.

The Academy suggested that in order to hurry things up, since there is so much at stake, further seeding experiments could be carried out among the typhoons of the western Pa- cific, where there are more typhoons than anywhere else in the world. They average more than twenty a year while the At- lantic annually has less than five hurricanes, most unsuitable for experiments.

If hurricane damage could be reduced only fifteen percent, the scientists said, it would pay the costs many times over.