Extreme convective precipitation in Liguria (Italy): a brief description and analysis of the event occurred on October 4, 2021

An extreme precipitation episode, occurred in Liguria region on October 4, 2021, is presented and discussed in the present paper. In particular, a series of V-shaped quasi-stationary convective systems repeatedly affected central and western Liguria producing impressive and, in some cases, unprecedented rainfall amounts (up to 378 mm in 3 h, 496 mm in 6 h, and 741 mm in 12 h). A peculiar feature of this case study is its occurrence and propagation downwind the Apennines Mountain range. The main characteristics of the event, in terms of synoptic and mesoscale triggering processes as well as its dynamics, are discussed. It is found that the larger moisture contribution seems to have a Mediterranean origin and a possible role of a cold pool generated in the first phase of the event in the evolution of the convective system is hypothesized. This paper follows a workshop on high-impact weather jointly organized by the newly formed Italia Meteo Agency and the Italian Association of Atmospheric Sciences and Meteorology (AISAM) in September 2022, to promote the sharing of the experiences among operational and research meteorological centers in Italy. The preliminary results presented here are intended to stimulate further work on the topic to gain a better understanding of the dynamics of such extreme precipitation events and to improve the predicting capability.