Water Wheel July/August 2020: Water Kidz

Abstract

Water Kidz Hail is one of the most amazing, and destructive, forms of precipitation we have in South Africa. Hail usually occurs during summer thunderstorms. A hailstone begins as a small water drop or a round snow pellet in a cloud. The drop grows by collecting many cloud drops. The little drop is blown by a strong wind inside the cloud to where it meets with some extremely cold water drops. These supercooled drops are still liquid water even though the temperature is below freezing. When the little drop mixes with these extremely cold drops, they join, and the little drop has now become a hailstone. The little hailstone is thrown up inside the cloud, still collecting other cold drops. The hailstone gets bigger and bigger until it goes to the top of the cloud. Then, because there is no more wind, it falls back down through the cloud. While it is falling it gets even bigger as it bangs into more supercooled drops. If it goes down very fast it can hit the earth at up to 144 kilometres per hour, bouncing like popcorn. Hail can only form in thunderstorm or Cumulonimbus clouds.

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