High resolution simulations of a flash flood near Venice
Other literature type
Miglietta, M. M.
(issn: 1684-9981, eissn: 1684-9981)
During the MAP D-PHASE (Mesoscale Alpine Programme, Demonstration of
Probabilistic Hydrological and Atmospheric Simulation of flood Events in the
Alpine region) Operational Period (DOP, 1 June–30 November 2007) the most
intense precipitation event observed south of the Alps occurred over the
Venice Lagoon. In the early morning of 26 September 2007, a mesoscale
convective system formed in an area of convergence between a south-easterly
low level jet flowing along the Adriatic Sea and a north-easterly
barrier-type wind south of the Alps, and was responsible for precipitation
exceeding 320 mm in less than 12 h, 240 mm of which in only 3 h.
The forecast rainfall fields, provided by several convection resolving models
operated daily for the D-PHASE project, have been compared. An analysis of
different aspects of the event, such as the relevant mechanisms leading to
the flood, the main characteristics of the MCS, and an estimation of the
predictability of the episode, has been performed using a number of high
resolution, convection resolving models (MOLOCH, WRF and MM5).
Strong sensitivity to initial and boundary conditions and to model
parameterization schemes has been found. Although low predictability is
expected due to the convective nature of rainfall, the forecasts made more
than 24 h in advance indicate that the larger scale environment driving the
dynamics of this event played an important role in favouring the achievement
of a relatively good accuracy in the precipitation forecasts.