In Situ Hail Observations Using a Rapidly Deployable Network of Hail Impact Disdrometers

The use of in-situ adaptive instrument networks has been successful in documenting storm-scale environments near and within supercell thunderstorms. Most instrument systems designed to capture hydrometeor distributions are not sufficiently rugged to survive repeated exposure to large hail or are cost prohibitive for use in a large, adaptive network. The Insurance Institute for Business & Home Safety (IBHS) developed a low-cost, rapidly deployable hail impact disdrometer probe which built upon previous work by Lane et al. (2002). The instrument employs an impact plate, piezoelectric disk, and a low-cost robotics microcontroller. The probe captures hail impact kinetic energies which are used to estimate approximate hail sizes. Probes can resolve hailstones of approximately 0.5 cm and larger. IBHS maintains a network of 18 probes, eight of which are equipped with thermodynamic measurement capability.

The network of impact disdrometers was deployed in 2017 during the annual IBHS hail field research program. The field research team was able to capture several quality datasets during the 2017 campaign in May and June. The work presented here summarizes the in-situ observations from the impact disdrometers and physical hail measurements from four supercell thunderstorms. In each case the spatial extent of the swath of hail was captured and provided a detailed picture of kinetic energy flux, estimated hail size, and hail concentrations and how these quantities evolved both spatially across the swath of hail and due to storm-relative location.