What is hail and how is it formed?



  • photo:Herman Hengelo;link:https://www.flickr.com/photos/h_hengelo/26410848438

    Any thunderstorm which produces hail that reaches the ground is known as a hailstorm. Hail is in essence, frozen rain. It only falls from a specific type of cloud called a cumulonimbus cloud also known as a thunderstorm cloud. Hailstones usually measure between 5 mm (0.2 in) and 15 cm (6 in) in diameter and fall anywhere a thunderstorm can form. Hailstone's larger than 2 cm (0.80 in) are usually considered large enough to cause damage.

    Hail is often confused with sleet. Sleet is rain containing some ice, usually seen with snow. Below is an image of sleet which has settled on the ground it's visibly different to hailstones on the ground due to sleet being more of a wet mulch.

    photo:Met Office;

    Hail formation requires environments of strong, upward motion of air within the thunderstorm, these tiny raindrops are carried upward by updrafts freezing levels of the atmosphere and form hailstones.

    photo:anti-grele.fr;link:http://www.anti-grele.fr/en/anatomy/

    These then sink back down in the cloud with added weight and are then carried back up by the updraft growing by colliding with liquid water drops and other smaller hailstones that freeze onto the hailstone's surface as if adding layers of layers of frosting to a cake but in a really lumpy random irregular way, then sinking and rising until the cloud can not contain it's weight any more.


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