Simulazione di un temporale a supercella con WRF-ARW: un caso studio sul Piemonte, Italia

This work investigates the possibilities of reproducing a supercell storm that occurred in Piedmont on 6 July 2023 using the mesoscale meteorological model WRF. The event, that hit the provinces of Asti and Cuneo (Italy) in the early afternoon, was characterized by intense rainfall, large hail and strong wind gusts. Using the ECMWF analyses as boundary conditions, three simulations were carried out using different microphysics parameterizations, aiming to observe how the scenarios produced by the model respond by changing the description of the physical processes within the clouds. In particular, the WSM6, WDM6 and Milbrandt 2-moment schemes were used. The results of the simulations were then compared with the data observed by the Arpa Piemonte meteorological station network, considering various physical variables or composite indices. Storm environments with features similar to those observed were reproduced, with inaccuracies in spatial and temporal localization. The greatest similarities with the observed data were found in the distribution and intensity of rain, hail, graupel and wind shear, when moving from a one-moment microphysics scheme to a two-moment microphysics scheme. In particular, using the WDM6 and Milbrandt 2-moment schemes, scenarios compatible with a supercell appear, with notable inaccuracies in the time scale. A qualitative comparison would therefore suggest that more complex schemes have a better chance of correctly reproducing the phenomenon, in contrast to statistical analyses on various station points which do not favor any performed simulation. In fact, on a statistical level, the performance of simulations with the most complex schemes seems to be penalized by poor temporal localization.