The Piedmont flood of 1994: An analysis of the concurrent meteorological processes based on systematic numerical experimentation

In this study, the BOlogna Limited Area Model (BOLAM III, Buzzi and Malguzzi, 1997) has been used to simulate the meteorological event that led to the flood of November 1994 in the Piedmont region. Two main areas of precipitation that contributed to the Piedmont flood can be identified in the period from 4 to 6 November. The first spell affected the area between the Maritime Alps, Ligurian Apennines, and the Langhe hills, and was characterized by embedded convective activity. The second rainfall maximum was observed on 5 and early 6 November over the eastern flank of the western Alps. Total precipitation exceeding 250 mm/day was reported in several stations in both areas, with a peak of 314 mm accumulated on the 5th over the northern Piedmont. The synoptic situation was characterized by a slow drift to the east of an upper level through whose axis extended from Central England to the Alboran sea, crossing north-western France and the Gulf of Lion. A double frontal structure was present at low levels, with a secondary weak trough in the msl pressure associated with a pronounced cyclonic shear in the low level wind, ahead the main trough. A more detailed description of this case is presented in Buzzi et al. 1998, hereafter referred to as BTM.