Slantwise circulations and convection in pre-frontal environment over central Italy: a numerical study

The synoptic situation over Central Italy on 30 October 2008 showed a strong south-westerly wind associated with a synoptic-scale trough and cold front passage. Bands of precipitation aligned with the wind developed well ahead of the front, combined with individual convective cells. Severe surface winds and pronounced wave trains in the lee of the Apennines were also observed. The above features were successfully simulated with the non-hydrostatic model MOLOCH at 0.9 km resolution. Idealized experiments without orography were then performed to isolate and diagnose the role of instabilities in the observed development, and the dynamical properties associated with the co-existence of conditional and symmetric instability, and a 'Delta-M-adjustment' event.