For those of us who live in areas where snow and ice is common, we’re used to frozen precipitation falling from the sky, but hail is much different. Large chunks of ice fall to the ground with great force, not during the winter, but during a warm weather season. It often accumulates on the ground and can take hours to melt. It can also cause incredible damage to crops, buildings, and people. To me, that makes hail one of the most interesting of all weather phenomena.
How Hail Forms
It doesn’t take a four-year degree in Physics to understand that rain falls out of the sky because the water droplets grow to a weight that makes it impossible for the air to support them, so how are chunks of ice supported by the air long enough to become the size of coins, golf balls, or, heaven forbid, baseballs?
Up, Up, and Away
Hail forms best when the storm has a high water content, a strong updraft, and a large portion of the cloud at a temperature below freezing. Supercooled water freezes on condensation nuclei, begins to fall, and the updraft forces the hail (the frozen water) back up into the clouds, where more supercooled water freezes on the hail.
The stone then falls toward the ground until it is forced upward again by the rising air of the updraft. This process repeats itself, with the hailstone rising and falling like ping pong balls inside of the lotto machine, until the stone is too heavy for the updraft to support it, at which time it crashes through the atmosphere and bounces off the newest car in the parking lot. With that process, of course, the stronger the updraft, the greater the potential size of the hail stones, some of which reach the size of softballs (4.5 inches in diameter).
–Paul Yeager
