Developing Probabilistic Hail Guidance from Multi-radar, Multi-sensor Data and High Resolution Hail Reports

The need to know the size of hail a storm is producing is important information during the storm's life for National Weather Service (NWS) warning operations. After a storm passes, information on the likely areas where hail of certain sizes fell is important not only for NWS warning verification but also for other non-meteorological users, such as insurers. Thus, there is a need not only for detecting hail and predicting size within a storm (i.e., detections aloft) but also to determine hail size at the surface for a given point. Previous research has shown significant overlap of parameter spaces between different hail sizes, which suggests the need to develop probabilistic tools and guidance. This study will use the Warning Decision Support System—Integrated Information (WDSS-II) and reports from the Severe Hazards Analysis and Verification Experiment (SHAVE) to explore both hail size estimates as a forecast and hail size estimates at the surface. Specifically, this study will explore: 1) probabilistic forecast projections along a storm's motion of different hail sizes; 2) probabilistic estimations of hail sizes at the surface following storm passage; 3) utility and accuracy of hail size estimates using both specific size estimates and binned sized estimates.