Comparison of Impact Disdrometer and Surface Hailstone Measurements with Dual-Polarization Doppler Radar-Based Hail Swaths from the 29 May 2018 Erick, Oklahoma Hailstorm

On 29 May 2018, two supercell storms merged and produced significantly severe hail (maximum size >3.25 in or >8 cm) in and around the town of Erick, Oklahoma. The storms moved over an array of 16 hail impact disdrometers deployed as part of the Insurance Institute for Business and Home Safety (IBHS) Hail Field program. In addition, teams from IBHS and Penn State made physical measurements of hailstones along the hail swath. These unique based observations provide an outstanding ground truth for radar-based inferences of hail size.

We compare the surface observations to popular hail detection and sizing products, including the Maximum Estimated Size of Hail (MESH) swath and the polarimetric radar Hail Size Discrimination Algorithm (HSDA), to the disdrometer and manually measured hail sizes and concentrations. The largest hail fell south of the MESH- and HSDA-indicated maxima, indicating a northward bias in these radar products owing to their failure to account for size sorting. Other novel polarimetric Doppler radar-based hail swaths are constructed (e.g., hail differential reflectivity, differential reflectivity columns, correlation coefficient updraft signature, radial velocity-inferred rotation tracks) and compared to the surface observations.