A Climatological Study of Hail Occurrence using the MRMS MESH Product

Traditional hail climatologies using only hail reports collected by the National Weather Service (i.e., Storm Data) have been found to contain inaccuracies in reporting locations and hail diameters. The use of remote sensing data, like the Multi-Radar Multi-Sensor (MRMS) Maximum Expected Size of Hail (MESH) product, to develop a hail climatology has been previously explored. Using spatially gridded data like MRMS, MESH allows for better spatial description of the hail climatology, as compared to past research methodologies using point storm reports. Temporally, remote sensing data does not suffer from observers being unavailable during nighttime hours. Previous research has shown the utility of MRMS products to define areas of categorical hailfall, thus the use of MRMS MESH is appropriate to generate a climatology.

CONUS-wide MESH data from 1998 through 2011 is available from the Multi-Year Reanalysis of Remotely Sensed Storms (MYRORSS) historical database of products. This study will expand on previous research, which used MESH data to develop a simple climatology of hail occurrence using a limited number of years of MESH data. This study will seek to explore the seasonal and hourly climatologies of hail occurrence, in addition to the environments (as defined by CAPE and bulk shear) in which different hail categories are associated. Regional variability will also be explored.

Initial exploration of using MESH and azimuthal shear concurrently produces a more robust metric for significant-severe hail. Ongoing work has shown that the distribution of azimuthal shear for storms producing hail exceeding 50 mm in diameter is distinct compared to the distribution of azimuthal shear from storms that do not produce hail exceeding 50 mm in diameter. Initial results of a significant-severe hail climatology combining MESH and azimuthal shear will be discussed.