Gazing inside a giant-hail-bearing Mediterranean supercell by dual-polarization Doppler weather radar

Abstract

Ongoing climate change is considered to be responsible for the intensification and increased frequency of extreme weather events. The Mediterranean basin is not exempted by such modification processes as testified by the recent increase in the number of severe convective storm and mesocyclones. In recent years this kind of events caused many victims and damages in the such area, due to its geomorphological configuration and to the massive urban development of the last decades. Due to their local-scale nature Mediterranean extreme events can hardly be forecast with the use of numerical weather prediction systems and cannot adequately observed by using satellite platforms. These methods are not as straightforward as those based on radar observations because their spatial-temporal resolution is not necessarily adequate to resolve exceptional atmospheric phenomena as a weather radar can indeed offer. This article uses weather radar observations of an exceptional Mediterranean hail-bearing supercell that hit the central-eastern coast of the Adriatic Sea on 10 July 2019 causing flash flood and giant hail. Two operational dual-polarization Doppler C-band radars, managed by the Civil Protection Department of Italy, were able to observe, in an operational framework, the genesis and the evolution of the supercell, allowing for a detailed analysis of the event. Exploiting the unique time-resolved high-resolution three-dimensional available measurements, the combined use of a wind-field retrieval scheme and the interpretation of the dual-polarization radar observed features reveals some unique microphysical processes, rarely documented through radar observations at the Mediterranean latitudes. Results of this work improve the understanding of mechanisms and processes of giant hail formation and it is crucial to improve the nowcasting and forecasting skill for the early detection of hazardous meteorological events.