A Comparison of Three Significant Hail Producing Supercells Sampled during HailSTONE Using S-Band Dual-Polarization Radar

The hail cores of three supercells were sampled by HailSTONE (A Hail Spatial and Temporal Observing Network Effort) on 21 May 2011 near Ada, Oklahoma, and 24 May 2011 near Eakly, Oklahoma. In these cases, convection originated in thermodynamic and kinematic environments that were characterized by surface-based convective available potential energy (CAPE) of 3000 J kg^-1, effective bulk shear in excess of 25 m s^-1, and hodographs supportive of supercells and tornadoes. Both supercells developed by mid to late afternoon and resided mainly over rural areas, contributing to a very low severe weather report density recorded in Storm Data; only two hail reports total.

HailSTONE operated for approximately 1 h during each respective supercell intercept, and was able to record specific information of the hail-fall character, including the maximum and average diameter and a general concentration of the hail stones across the hail swath. This field effort led to a total of 188 hail reports: 116 from the Ada supercells and 72 from the Eakly supercell. Detailed sampling revealed a maximum hail diameter of 7.62 cm (3 in.) with each storm, as well as multiple instances of significant (diameter ≥ 5.1cm; 2 in.) hail. Additionally, the location and the concentration of the biggest hail were analogous in each supercell.

Both the Ada and Eakly supercells were also observed by the S-band dual-polarization radar in Norman, Oklahoma (KOUN), making a comparison of traditional and polarimetric variables possible. Strong similarities in the spatial distribution of hail, observed hail sizes, and environments of these supercells suggest that their radar presentation may also be similar; thus, this study will compare a host of both single- and dual-polarization radar signatures between the two storms and to the signatures expected for significant hail-producing supercells. Ultimately, this study seeks to assess the overall structure of both supercells, to quantify polarimetric variables associated with each storm, and to discuss the ways in which these storms validate and/or challenge the conceptual model of dual-polarization signatures for significant hail-producing storms.