Analysis of RaXPol and In-Situ Hail Impact Disdrometer Data in a Hail-producing, Left-moving Supercell in Colorado

The University of Oklahoma’s RaXPol mobile, dual-polarimetric research radar and the Insurance Institute for Business & Home Safety’s (IBHS) deployable network of hail impact disdrometers were successful in sampling a hail-producing, left-moving supercell near Kiowa, Colorado on 13 June 2016. The RaXPol radar was deployed four miles southwest of Ramah, Colorado and collected data from 2152 - 2218 UTC. Four hail impact disdrometers were deployed in advance of the targeted convective storm to the north-northwest of the radar. The western-most probe was located approximately 13 km east-southeast of Kiowa. Radar observations indicated a defined anti-cyclonic circulation aloft along the northwest portion of the echo as it passed to the west of the radar and crossed the disdrometer array.

Physical measurements of hail following the passage of the thunderstorm identified a maximum hail size of 3.9 cm to the west of the array of disdrometer probes. Three of the four probes captured hail impacts with peak bulk concentrations approaching 80 particles s^-1 m^-2 at the two western-most probe locations. Physical and disdrometer observations indicated that maximum hail sizes decreased from west to east while bulk concentrations increased until an abrupt end in hailfall between the two eastern-most disdrometers. Hailstones along the western side of the swath were primarily defined by clear ice through wet growth processes and were irregular in their shape. Hailstones transitioned to spheroidal shapes with typical alternating clear and opaque (bubble-filled) layers by the western-most disdrometer probe.   This presentation will discuss the mobile radar observations and their relation to hail observations at the ground, as well as the characteristics of the measured hailstones.