Evaluating a Hail Size Discrimination Algorithm for dual-polarized WSR-88Ds using high-resolution reports and forecaster feedback

The National Severe Storms Laboratory has developed a Hail Size Discrimination Algorithm (HSDA) for the dual-polarized WSR-88D network. The HSDA currently uses three radar fields (reflectivity, differential reflectivity and correlation coefficient) and radar beam heights with respect to the melting layer and -25 degree Celsius wet bulb temperature height. The algorithm is currently ongoing evaluation through two methods. The first is a quantitative analysis of performance using high-resolution hail reports from the Severe Hazards Analysis and Verification Experiment (SHAVE). SHAVE on average collects reports every 2 km along a storm's path, including reports of ‘no hail' and non-severe hail sizes (< 25 mm diameter). The second evaluation method is occurring within NOAA's Hazardous Weather Testbed/Experimental Warning Program (HWT EWP). The HWT EWP allows for scientist to bring research products into a quasi-operational setting for evaluation by National Weather Service forecasters. This presentation summarizes skill scores from the SHAVE report comparisons, examples of algorithm performance in different storm and different near-storm environments and summaries of forecaster evaluations from the HWT EWP.