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Sarah Raders, age 13, of Clendenin, W. Va., for her quustion:

What is a cloudburst?

No, a cloudburst is not a big, bursting bag of water. Though this is what seems to be the case if you are unlucky enough to get caught in one. The rain comes down in a deluge, as though a giant pail of water were suddenly emptied from the sky. The water falls too fast to run off in the streams and gutters. In a few minutes the ground is swamped and flooded. There is water under foot and streams falling from above.

A real cloudburst is a very rare weather event, which is lucky for us. It never lasts long and it covers only a small area. Letts say that a cloudburst covered one square mile and dumped an inch of rain in ten minutes. More than 72,000 tons of water would land on the ground. This storm would certainly rate as a cloudburst, for only a quarter of an inch of water in five minutes is rated as excessive rainfall.

It is hard to imagine thousands of tons of water suspended in a cloud above the ground. But 113 tons of water are needed to douse each acre with an inch of rainfall 72,300 tons necessary to pour one inch upon each square mile. As a rule, this mammoth weight of water is not all suspended in the dark cloud before the shower. When rain making starts in a cloud, damp air flows in from surrounding areas, bringing more moisture to be turned into rain. This process goes on during a long, steady rainfall. Raindrops form and fall while a new batch of raindrops is forming.

In a cloudburst there is a bottleneck in the operation. The raincloud rests on a column of warm, rising air. The updraft is strong enough to keep the newly made raindrops from falling. Meantime, more batches of raindrops are being made in the cloud. These too are held aloft by the rising current of air. Tons and tons of water accumulate in the cloud.

At last the mountain of water becomes so heavy that the rising air can no longer support it. The accumulated raindrops break through and down comes the deluge. The cataracts of failing water are the stored raindrops which should have been falling steadily for the past hour.

Runoff streams and gutters are designed to carry off steadily falling rain. The deluge of a cloudburst is too much for them. So the water slops all over the ground, causing flash floods and property damage. fierce storm in the hills also may slop over the stream beds and cause a flash flood, This storm is sometimes called a cloudburst though it is not properly one. The extra water on the ground is caused by the flooding runoff from the hills. A true cloudburst comes down from above. These falling torrents from the sky are greater than excessive rainfall ‑which is rated as a quarter of an inch in five minutes, one inch in an hour or two and one half inches in 24 hours.

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