The 1966 century flood in Italy: a meteorological and hydrological revisitation

The widespread flood event that affected northeastern and central Italy in November 1966, causing severe damages to vast populated areas including the historical towns of Florence and Venice, is revisited with a modeling approach, made possible by the availability of the ECMWF global reanalysis (ERA-40). A simulated forecasting chain consisting of the ECMWF global model, forcing a cascade of two mesoscale, limited area meteorological models apt to reach a convective resolving scale (about 2 km), is used to predict quantitative precipitation. A hydrological model, nested in the finer-scale meteorological model, is used to reproduce forecasted flood hydrographs for different river basins of the investigated areas. Predicted precipitation is in general very sensitive to initial conditions, especially when associated with convective activity, such as over central Italy, in the Arno river basin. Orographically enhanced precipitation, e.g., the one predicted in the eastern Alps, is quite stable and in good agreement with observations. Hydrological forecasts, made separately in different river basins, reflect the accuracy of the simulated precipitation.