How Are Large Hailstones Produced in Five Distinct Potential Severe Hailstorm Environments?

Abstract The thermodynamic and kinematic environments favoring the growth of large hailstones (diameter ≥ 19 mm) may be classified into five distinct types. In this study, we present a simple semi-three-dimensional hailstone growth trajectory model and explore the respective microphysical mechanisms of large-hailstone production (LHP) under these five types of environments. Type 1 environment is characterized by the strongest updraft and adequate cloud water supply in tropical plains. This type has the highest growth rates for embryos and surpasses the greatest melting loss among all five types of environments. Type 2 over tropical hills has a deeper updraft with greater growth at high altitudes. Type 3 over midlatitude plains is characterized by a relatively thick growth zone and the second-highest growth rate. Type 4 over high-latitude plains has a high mass growth during ascent but a medium descent growth rate on average. Over elevated terrains, type 5 has the shallowest melting zone and the lowest melting rate, allowing hailstones to reach the surface with the least mass loss. The responses of hailstone growth to initial hailstone embryo heights are type dependent but are insensitive to initial hailstone radii. A longer ascent (descent) growth duration leads to a greater mass increment and a higher potential for low (high)-level-seeded embryos to grow into large hailstones. Sensitivity tests show that kinematic conditions measured by wind shear are important in all types. Strong wind shear serves as a preferable environment for hailstone growth across five types by extending the growth duration.