Applications of MRMS 1-h Swath Data and High-Resolution Hail Reports for Developing an MRMS-Based Hail Climatology

The Multi-Year Reanalysis of Remotely Sensed Storms (MYRORSS) is a large data set of Multi-Radar, Multi-Sensor (MRMS) data for the years 1998 through 2011. MYRORSS data include a three-dimensional reflectivity grid, along with reflectivity-derived products like Maximum Expected Size of Hail (MESH), and two layer-maximum azimuthal shear products. Previous work has focused on strictly using maximal accumulations of MESH and thresholding that data to develop a radar-based hail climatology. However, other work has shown the limitations in using MESH thresholds exclusively, and MRMS product thresholds in general for identifying areas of surface hail fall. These previous efforts to evaluate MRMS for surface hail fall identification have used high-resolution hail reports from the Severe Hazards Analysis and Verification Experiment (SHAVE). Currently, a volume-by-volume radar analysis for a subset SHAVE cases is ongoing. A summary of the 2000+ volumes analyzed thus far has shown that peak azimuthal shear values along a storm track can help greatly in determining whether a storm produced significant-severe hail, which is a major shortcoming of using reflectivity-based MRMS grids exclusively for surface hail fall identification.

This presentation will explore using 1-hr swath data from MRMS to determine the characteristics of storms for classifying surface hail fall. MESH swaths will be clustered using a watershed-based technique and then these clusters will be used to summarize other MRMS products within that cluster’s boundaries. These methods will be applied to the SHAVE database of 731 cases; the maximal and common hail sizes, in addition to counts of hail size categories, will be compared to the overlapping cluster. The results of the SHAVE analysis will be applied to the MYRORSS data to evaluate the impact of the change in developing an MRMS-based hail climatology using 1-hr swaths with characteristics versus a climatology purely based on grid point-by-grid point MESH.