Weather Tidbits: Hail Formation

This edition of Weather Tidbits will be discussing how hail forms. Two critical factors for hail formation is the strength of an updraft within a thunderstorm cloud and the height of the freezing level. Hailstones form when the updraft carries the water droplet into the freezing layer. The droplets eventually freeze and are continuously suspended in the air by the updraft. As this happens, additional layers of ice form each time it is swept up. Eventually, the weight exceeds the force of the updraft and the hailstone falls. The thunderstorms with the largest hailstones will feature very strong updrafts and a low height freezing level. The amount of dry air aloft can dictate the level of the freezing layer because dry air cools efficiently. This process is most common with thunderstorms, which is why you don’t see hail during the winter. It’s a very different process from sleet formation.