Insights Into Identifying and Nowcasting Deep Hail Accumulations

This presentation will highlight some of the first results of the Colorado Hail Accumulation from Thunderstorms (CHAT) project. A dual-polarization radar-based hail accumulation algorithm for operational applications has been developed and validated for the Colorado Front Range using 20 quality-controlled hail depth reports. The hail accumulation algorithm shows promise for reported accumulations larger than 3 cm, where radar derived accumulations remain within a ratio of 1.5 between radar-derived and reported accumulations. Furthermore, we assess the relative importance of in-cloud hail production, storm speed, and melting rates in determining the amount of hail accumulation observed on the ground using the improved hail accumulation algorithm combined with lightning and dual-polarization radar data from a set of 32 thunderstorms. This assessment is the first step towards a nowcasting algorithm for deep hail accumulations. Our results show that radar-derived in-cloud hail production is the most correlated to hail accumulation. In contrast, while storm speed and melting rates alone show little to no correlation to hail accumulation, both are determined to be important when comparing storms that experience similar in-cloud hail production.