Radar-derived Convective Features and Atmospheric Environments of Hail-Producing Storms over the Contiguous United States

Abstract Hail smaller than 0.75 inch is known to cause economic impacts yet remains understudied due to report biases towards recording larger hail sizes (≤1 inch). In this study, we assembled ground hail reports during 2017-2022 from the National Centers for Environmental Information (NCEI) Storm Data, Community Collaborative Rain, Hail and Snow Network (CoCoRaHS) and Meteorological Phenomena Identification Near the Ground (mPING) databases. Then these reports are collocated with the attributes of radar-derived convective features from the Multi-Radar/Multi-sensor System (MRMS) and the European Centre for Medium-Range Weather Forecasts Reanalysis v5 (ERA5) atmospheric vertical profiles to construct a dataset describing properties of a full spectrum of hailstorms. The characteristics of radar reflectivity and atmospheric profiles are examined for hail of different sizes reported within selected regions over the Contiguous United States (CONUS). In addition to the seasonal and diurnal variations, the morphology of convective features shows apparent regional differences from west to east in CONUS. The Maximum Expected Size of Hail (MESH) performance against reported hail sizes shows underestimation of hail with significant sizes, and overestimation of small hail sizes. ERA5 vertical atmospheric profiles are explored to form relationships between storm environment and hail sizes. In addition to the relationships between wind shear and hail sizes, the roles of low-level relative humidity and freezing level height in regard to hail melting are discussed.