Review of impact factors of the velocity of large hailstones for laboratory hail impact testing consideration

The terminal velocity of hailstones is an essential quantity in hail research. It is an important value for the kinetic energy of hailstones and has to be carefully considered when laboratory hail impact testing is being planned. Many standardized hail impact testing procedures require specific impact velocities. Several empirical models for various hailstone diameter ranges have been developed to calculate the velocity based on the diameter, indicating somewhat inconsistent results. The velocity is influenced by factors such as their density, drag coefficient, shape or air density, and strong winds. This article takes a closer look into each of these factors and how they influence the velocity of hailstones and the damage potential of hailstorms. Implications are made for laboratory testing of hail impact testing procedures and how the geographic location of hailstorms might be a considerable factor when designing a test.