An Extended Hail Climatology for Sydney, Australia, Derived from a Storm Database, Radar Reflectivity, Reanalysis, and Sounding Data

Severe hailstorms are a frequent occurrence in the eastern New South Wales region of Australia, and are one of the costliest natural disasters experienced in the area. An example of this was Sydney’s most recent severe hail event which occurred on 20^th December 2018 and resulted in an economic loss of approximately $1.189 billion dollars. Understanding the spatiotemporal distribution of severe hailstorm development is crucial for identifying the occurrence of hailstorm hotspots, changes in hailstorm distribution and frequency, and for improving forecasting capabilities. While Sydney is the most populated city in Australia, research into hailstorm development over the region and the mechanisms of formation are not extensively studied. Here, an extended and comprehensive climatology of the Sydney metropolitan region is presented, spanning the years 1950 to 2018. An observational database will be utilised to identify hail days and is supported by single-polarization volumetric radar observations in which daily maximum expected size of hail (MESH) grids are produced. Identification of potential hailstorm days through analysis of environmental parameters including CAPE, wind shear, freezing level and helicity will be computed using dynamically downscaled high-resolution (10 km) regional reanalysis (NSW and ACT Regional Climate Modelling, NARCliM) data and archived upper-air soundings.