The Lightning and Dual-Polarization Radar Characteristics of Three Hail-Accumulating Thunderstorms

Thunderstorms that produce significant hail accumulations at the surface impact residents by obstructing roadways, closing airports, and causing localized flooding from hail-clogged drainages. Storms that produce significant hail accumulations, sometimes in excess of 50 cm, have recently gained the interest of the scientific community. However, identifying these storms in real-time remains difficult in part because observable differences between these storms and storms that produce non-impactful hail accumulations have yet to be identified. Similarly, the characteristics within a single storm that are useful to quantity or predict hail accumulations at the surface are not understood fully. This study uses lightning and dual-polarization radar data to characterize hail accumulations from three storms that occurred on the same day along the Colorado/Wyoming Front Range. Each storm produced a maximum hail accumulation of 22 cm, 7 cm, and no accumulation. The magnitude of surface hail accumulations is found to be dependent on a combination of in-cloud hail production, storm translation speed, and hailstone melting. The optimal combination for substantial hail accumulations is elevated in-cloud hail production, slow storm speed, and limited hailstone melting. However, during periods of similar in-cloud hail production, lesser accumulations were observed when storm speed and/or hailstone melting was sufficiently large. These results will aid forecasters in identifying in real-time when hail accumulations are occurring.