The roiling clouds grow darkly thicker. Lightning rips the sky and thunder rumbles across the heavens. A cold wind gathers, sending waves through the wheat field. The first drops of rain splatter on the ground, rapidly increasing. The rain fuses into a cloudburst of hail.

Minutes later the wheat lies flat on the ground, sodden and shattered. The farmer's work for the year is lost.

In the United States alone hail causes up to $300 million damage each year, about equally divided between crops and property. Wichita, Kansas, one year had two hailstorms in twenty-four hours that cost between $9 million and $14 million

Hitting all over the country, hail ruins more crops than any other kind of storm. In certain parts of the Great Plains, it routinely destroys between eight and ten percent of all crops annually. Corn and wheat especially suffer from hail. because these crops are grown in so many places, including the Mississippi Valley, the "nation's breadbasket," where the hail is the worst.

Few things that grow are able to withstand these icy onslaughts from the clouds. Apples, peaches, plums, pears, apricots, grapes-all are vulnerable. Even the small hailstone leave these fruits pitted and bruised, making them unfit for market.

But hailstorm damage goes far beyond crops. Denver once needed twenty carloads of glass to repair greenhouses after a hailstorm had passed. A hailstorm at Pueblo shattered 10,000 windowpanes and drove holes in 2,000 roofs, letting in the rain that came with the hail. Hail smashes automobile wind shields, dents hoods, fenders, and tops. Airplanes encountering hailstorms often have to be scrapped.

Considering the size hailstones sometimes reach, their power to destroy is not surprising. In the laboratory cold room of the National Center for Atmospheric Research at Boulder, Colo rado, rests a hailstone 17.5 inches around. This monster fell at Coffeyville, Kansas, the state that loses the most from hail because of the damage to the wheat, its leading crop. A hailstone weighing a pound and a half crashed to earth a Potter, Nebraska, one July day in 1928 during a storm so violent that the hailstones made hissing sounds as they came down, burying themselves in the ground. The largest hailstone on record belongs to Troy, New York. This one measured five by five inches and tipped the scales at four pounds.

Hailstorms with stones as large as golf balls-or even baseballs -are not uncommon. Such a storm bombarded three counties in Kansas for a half hour on August 1, 1954, leaving the area covered with hail washed into drifts by the rain that came with it. One drift in a cornfield was 200 feet long, 70 feet wide, and 3 feet deep.

Thanks to space age science, the scourge of hail may soon be gone. "Of all the severe storms plaguing humanity, the hailstorm appears to be the most manageable," says Guy G. Goyer of the NCAR at Boulder, Colorado.

First of all, hailstorms are usually easy to identify. They are out in the open where they can be seen rather than skulking inside or behind something else, as for example tornadoes do.

Hailstones are simply frozen rain. They froze from being too long inside supercooled clouds. They were kept there by the updrafts that characterize the interior of thunderstorms. Carried upward into progressively colder levels at sixty to one hundred feet a second by these drafts, a freezing water droplet keeps going until it gets so big that gravity overcomes the force of the wind and it starts to fall. Thus hailstorms are born.

There is usually hail in any cloud with temperatures ranging down from nine points under freezing to four below zero. And the hailstones found here are the big ones.

Keeping the hailstones small can be done by seeding the clouds with silver iodide. Then either they melt on the way to earth or they arrive on the ground so tiny that they are harm less.

The effectiveness of silver iodide as a weapon against hail was first demonstrated by lrving Krick, the pioneer cloud seeder from the California Institute of Technology, who was decorated for his forecasting work in World War II. It was Krick and his team of experts from Caltech who made the critical six-day forecast needed for the invasion of Normandy.

Following early experiments, Krick seeded hail-bearing clouds for the grain farmers of southern Alberta in Canada probably the most hail-plagued region on earth. For forty years, by the records of the Alberta Hail Insurance Board, the grain farmers had lost on the average nearly thirteen percent of their crops each year to hail. Sometimes it killed their cattle as well. Hail insurance was getting so costly that the farmers couldn't afford it.

Krick's seeding of the hail clouds with silver iodide elimi nated the hailstones entirely or greatly reduced them in size. Grain losses from hail fell to almost nothing compared to what they had been. This reduction, along with the extra rain brought by the seeding, meant millions of dollars of extra income for the farmers.

By mid-1974 research and experimentation to improve the techniques of using silver iodide as a weapon against hail was going forward in a half dozen countries. The Russians used two systems for getting the silver iodide up to where they wanted it. One involved cannon, the other rockets.

The guns, firing shells filled with the seeding agent, de- livered the load farther away and higher up, but rockets carried a heavier load dispersing the nuclei either along a curving ballistic arc as they flew through the storm, or spewing it out vertically as the rocket casing came down by parachute.

Either way, the Russians told visiting American scientists they were getting good results. In the space of two and a half million acres they claimed three to five times less damage from hail than in another area where there was no seeding. Also, the seeding was inexpensive, costing only two or three percent of the crop's value. Elsewhere, the Russians reported, hail damage in a seeded area was less than one eighth what it was in the control area.

The Russians claimed they already knew all they needed about cloud-seeding against hail and were well into putting the knowledge to work.

In Kenya, too, there were big-scale experiments to control hailstorms, which were taking a heavy toll of the tea crop each year. Like the Russians, the Kenya experimenters first used rockets, but loaded with TNT rather than a seeding agent, firing from a network of positions inside the tea plantation.

While the Russians in their operations began firing as soon as radar identified the spot in the cloud where the hail was likely to be, the Kenyanese experimenters held their fire until the hail began falling. Then they kept the rockets going until the hail stopped. During sixty hailstorms they fired nearly five thousand rockets.

Apparently the rocket barrages worked. The plantation where they were fired from had the lowest tea losses of any.

The Kenya hail fighters then changed tactics, switching to silver iodide delivered by ground generators and airplanes, This brought good results too. In 223 seeded hailstorms, the average loss per storm was 2,863 pounds of tea. In 637 hailstorms not seeded, the average loss per storm was 6,894 pounds of tea.

As the news of foreign success with hail control kept com- ing in, particularly Krick's work in Canada, American scien- tists took increasing notice. The claims from abroad, they agreed, were not implausible. They decided it was high time they got down to a serious program of hail research of their own.

The National Science Foundation thereupon organized the National Hail Research Experiment, the largest program of its kind ever undertaken anywhere in the world. In full swing by 1972, the work was to last five years and the experiments were being carried out where the hail is worst-"Hail Alley" -where Colorado, Wyoming, and Nebraska come together.

With this project, which was under the direction of NCAR, scientists hoped to clear up once and for all the questions which had kept them divided so long. They had many new instruments to work with, cutting down the guesswork, and they planned to start with a long period of observation which hadn't been possible before.

At the same time they were out in the field watching nature in action the scientists would also be busy in the laboratory building a mathematical model of a hailstorm. With such a model they could calculate the effects of seeding on the forma tion of hail and on the storm's behavior.

A major aim was to develop and test various techniques for hailstorm modification. First they wanted to try out the gun and rocketry methods of the Russians. "It is essential," said the National Academy of Sciences, "that the Soviet hail- storm seeding procedures be tested as soon as possible."