In the past year, San Antonio has experienced several devastating hailstorms resulting in millions of dollars in damages. We are all aware of the destruction a hailstorm can cause, but do you know how hail is formed inside of a thunderstorm?
How is Hail Formed?
Within a thunderstorms, very fast currents of air move upwards and downwards. Those currents are called updrafts and downdrafts. Inside the updrafts, water vapor and rain are pushed extremely high into the clouds where the air temperature drops below freezing. The rain and water vapor freezes and condenses, producing a tiny ice particle which serves as the center of the hailstone.
Eventually, the tiny ice particle is pulled back below the freezing line by gravity. As it falls, the ice particle collides with rain drops and accumulates a layer of water around it. The particle is then carried back above the freezing line by updrafts causing this new layer to freeze and the hailstone to grow.
The hailstone undergoes this up-and-down cycle within the thunderstorm until a downdraft pushes it to the ground or until it grows too heavy for an updraft to overcome the force of gravity.
Sizes of Hail
Hail comes in varied sizes. Smaller hail is about pea sized, where as larger hail is around the size of a golf ball. Occasionally, storms will produce hailstones the size of a softball.
According to the National Weather Service, in order for a thunderstorm to produce golfball-sized hail, its updraft speed would need to be at least 56 mph. Softball-sized hail requires strong updrafts that blow more than 100 mph.