Evaluation of the WRF-HAILCAST Modelling System to Forecast Hail Episodes During August 2022 over Catalonia (Spain)

Abstract

During August 2022, several significant hail events were recorded in Catalonia (Spain), including 12 cm hail on the 30th, the largest size ever documented in Spain. This study evaluates the performance of the HAILCAST model coupled with WRF for these hail episodes. The model output has been compared with information from the Catalan Meteorological Agency (SMC) and with reports from the European Severe Weather Database (ESWD) including their observed sizes and locations. Daily HAILCAST maximum hail diameter fields were analyzed, together with accumulated hail simulated by WRF. Moreover, the events of 17, 21 and 30 August were selected for a further analysis, comparing the HAILCAST maximum hail size, accumulated hail from WRF working without HAILCAST, and WRF-simulated accumulated precipitation with precipitation from ERA5-Land, GPM IMERG product and observations from local stations. The results show that HAILCAST can substantially overestimate both the size and spatial extent of hail, with predicted diameters reaching up to 25 cm at specific points in the domain. The model’s ability to generate convection can be observed, which is closely related to the HAILCAST output. Overall, HAILCAST proves to be promising for hail forecasting, but its performance is tightly constrained by the convective activity produced by WRF.