A Hybrid Single-/Dual-Polarization Hail Detection and Sizing Algorithm for the WSR-88D

Recently two different hail detection schemes have been deployed to National Weather Service operations: the Multi-Radar, Multi-Sensor (MRMS) system and the Hail Size Discrimination Algorithm (HSDA).  The MRMS uses a 3D reflectivity grid blended with environmental information to create hail size estimates across the entire CONUS using the Hail Detection Algorithm (HDA) process, which is currently deployed on the WSR-88D but runs on a storm cell-by-storm cell basis not a grid point-by-grid point basis.  The HSDA runs on individual WSR-88D radars, within the Hydrometeor Classification Algorithm (HCA), to create hail size estimates on each elevation scan within the radar’s domain.  While both the MRMS and HSDA data represent an upgrade to the current HDA since both provide estimates to spatial extent of hail fall, the creation and delivery methods of the MRMS and HSDA are different.  HSDA runs on the individual radar, while MRMS is centrally located and then distributed to field offices.  Thus, problems in communication in delivering MRMS grids could lead to inconsistencies in operational awareness.  An effort is underway at NSSL to develop a hybrid hail detection algorithm.  This effort has adapted the HDA technique to run on a voxel-by-voxel basis on single radar data to create hail size estimates.  The results of the accuracy of this algorithm set-up will be presented.  Investigations and discussions on how the single- and dual-polarization algorithms can be blended and comparisons to MRMS hail estimates will also be presented.