12 September 2012: A supercell outbreak in NE Italy?

Abstract

On 12 September 2012 a sequence of convective events hit the northeastern part of Italy and in particular the eastern part of Veneto and the plain of Friuli Venezia Giulia regions. During the day at least two events could be classified as supercells, the first one being also associated with a heavy hailfall. After a few hours, a third storm system, resembling a squall-line, although of limited dimensions, swept over the area.This event occurred during the first Special Observing Period (SOP1) of the HyMeX project as IOP2 (Intense Observing Period) and – also for this reason – many observations managed by different institutions were collected, including Doppler radar, extra-soundings, sodar and surface stations. Moreover, EUMETSAT was conducting its first experimental 2.5-minute rapid scan with the MSG-3 satellite, with data available from early morning until 0900 UTC of the IOP2 day.Several mesoscale models were run during the HyMeX SOP to support the field operations. A comparison between simulations of two high-resolution models (MOLOCH and WRF) is presented here and shows the capability in forecasting the intense convective activity in the area, although the exact temporal evolution of the systems was missed. Model simulations also provide useful insights concerning the mesoscale conditions conducive to the development of the convective systems.Finally, a diagnostic tool (Corfidi and Bunkers vectors) is applied using the model wind field, in order to infer further information on the temporal evolution of the convective cells.