How Is Hail Formed
How many times have you watched a hail shower or hail storm and wondered how the hail is actually formed? Well, here is a straight forward answer to this commonly asked question.
Hail or hail stones are irregular shaped balls or lumps of ice that fall from storm clouds when the right conditions exist. They are generally formed at the leading edge of a storm system in cumulonimbi clouds (thunder clouds).
Strong upward motion of air at this leading edge of a storm, combined with conditions which lower the freezing point, mean that water droplets freeze and instead of falling to the ground are cycled back upward. (The water droplets are originally formed, as with rain, when water condenses around dirt or dust particles in the air.)
During this upward journey they colide with and pick up more water droplets which themselves freeze around the original ball of ice, then fall again, are lifted again, attach to more droplets, and so on and so forth with each cycle. In larger, more powerful storms/updrafts, multiple hail stones can themselves become joined, forming even larger stones.
When the weight of the hail stones becomes too heavy for the updrafts of air keeping them aloft, they fall to the ground as hail. Lighter hail stones will not normally cause damage unless they are in extremely large quantities, thus perhaps causing local flooding by blocking drainage, or perhaps causing road accidents due to poor visibility.
In general, the more powerful the storm front updrafts (as in the case of a tornado producing storm for instance), the larger the size of the hail stones, as the power of the updrafts is able to cycle heavier and heavier stones before their weight becomes too much to hold them aloft any longer. These types of hail stones can cause massive damage to buildings, cars and even people caught out in the open in a storm. You can imagine what one large ball of ice travelling toward the ground at many miles per hour can do; now multiply that by the thousands or millions that may fall during one severe storm and the damage can become truly devastating.
According to the National Geographic News, the largest recorded hail stone in US history fell in Nebraska in June 2003. This hail stone measured some 17.8 cm wide. That’s roughly the size of a soccer ball.