Simulating Hail and Lightning Over the Alpine Adriatic Region-A Model Intercomparison Study

Hail is a significant convective weather hazard, often causing considerable crop and property damage across the world. Although extremely damaging, hail still remains a challenging phenomenon to model and forecast, given the limited computational resolution and the gaps in understanding the processes involved in hail formation. Here, eight hailstorms occurring over the Alpine-Adriatic region are analyzed using simulations with the Weather Research and Forecasting (WRF) and the Consortium for Small Scale Modeling (COSMO) models, with embedded HAILCAST and Lightning Potential Index (LPI) diagnostics at kilometer-scale grid spacing (& SIM;2.2 km). In addition, a systematic model intercomparison study is performed to investigate the ability of the different modeling systems in reproducing such convective extremes, and to further assess the uncertainties associated with simulations of such localized phenomena. The results are verified by hailpad observations over Croatia, radar estimates of hail over Switzerland, and lightning measurements from the LINET network. The analysis reveals that both HAILCAST and LPI are able to reproduce the affected area and intensities of hail and lightning. Moreover, hail and lightning fields produced by both models are similar, although a slight tendency of WRF to produce smaller hail swaths with larger hailstones and higher LPI compared to COSMO is visible. It is found that these differences can be explained by systematic differences in vertical profiles of microphysical properties and updraft strength between the models. Overall, results are promising and indicate that both HAILCAST and LPI could be valuable tools for real-time forecasting and climatological assessment of hail and lightning in current and changing climate.

Automated summary

Hail is a significant convective weather hazard, and it is challenging to model and forecast due to limited computational resolution and gaps in understanding hail formation. This study analyzes eight hailstorms using simulations and model intercomparison to assess the ability of different modeling systems in reproducing convective extremes. The results indicate that both HAILCAST and LPI are valuable tools for real-time forecasting and climatological assessment of hail and lightning in current and changing climate.