The disastrous storm of 4 November 1966 on Italy

Abstract

This is the first modeling reconstruction of the whole aspects (both meteorological and oceanographic) of the storm which hit Italy on 4 November 1966, producing 118 victims and widespread damages in Tuscany, at the northern Adriatic coast and in the north-eastern Italian Alps. The storm was produced by a cyclone which formed in the western Mediterranean and moved eastward towards Italy, reaching the Thyrrenian Sea, and then northward. The most peculiar characteristic of the storm has been the strong zonal pressure gradient and the consequent intensity and long fetch of the south-easterly sirocco wind, which advected a large amount of warm moist air, and determined exceptional orographic precipitation over Tuscany and the north-eastern Alps. The funneling of the wind between the mountain chains surrounding the Adriatic basin further increased the wind speed and determined the highest ever recorded storm surge along the Venetian coast. This study shows that present models would be able to produce a reasonably accurate simulation of the meteorological event (surface pressure, wind and precipitation fields, and storm surge level). The exceptional intensity of the event is not suggested by single parameters such as the sea level pressure minimum, the wind speed or the total accumulated precipitation. In fact, the precipitation was extreme only in some locations and the pressure minimum was not particularly deep. Moreover, the prediction of the damages produced by the river run-off and landslides would have required other informations concerning soil condition, snow coverage, and storage of water reservoirs before the event. This indicates that an integrated approach is required for assessing the probability of such damages both on a weather forecast and on a climate change perspective.