Water Vapor Sources of the October 2000 Piedmont Flood

Abstract

Abstract Very intense mesoscale or synoptic-scale rainfall events can occasionally be observed in the Mediterranean region without any deep cyclone developing over the areas affected by precipitation. In these perplexing cases the synoptic situation can superficially look similar to cases in which very little precipitation occurs. An example is the major precipitation and flooding event that affected Piedmont, Italy, between 13 and 16 October 2000. The emphasis of this study is on the moisture origin and transport. Moisture balances are computed on different space and time scales, revealing that precipitation exceeds evaporation over an area inclusive of Piedmont and the northwestern Mediterranean region, on a time scale encompassing the event and about 2 weeks preceding it. This is suggestive of an important moisture contribution originating from outside the region. A synoptic and dynamic analysis is then performed to outline the potential mechanisms that could have contributed to the large-scale moistur...