Overview of the first HyMeX Special Observation Period over Italy: Observations and model results

The Special Observation Period (SOP1), part of the HyMeX campaign (Hydrological cycle in the Mediter- ranean Experiments, 5 September–6 November 2012), was dedicated to heavy precipitation events and flash floods in the western Mediterranean, and three Italian hydro- meteorological monitoring sites were identified: Liguria– Tuscany, northeastern Italy and central Italy. The extraordi- nary deployment of advanced instrumentation, including in- strumented aircrafts, and the use of several different opera- tional weather forecast models, including hydrological mod- els and marine models, allowed an unprecedented monitoring and analysis of high-impact weather events around the Italian hydro-meteorological sites. This activity has seen strong collaboration between the Italian scientific and operational communities. In this paper an overview of the Italian organization during SOP1 is provided, and selected Intensive Observation Periods (IOPs) are described. A significant event for each Italian target area is chosen for this analysis: IOP2 (12–13 September 2012) in northeastern Italy, IOP13 (15– 16 October 2012) in central Italy and IOP19 (3–5 Novem- ber 2012) in Liguria and Tuscany. For each IOP the mete- orological characteristics, together with special observations and weather forecasts, are analyzed with the aim of high- lighting strengths and weaknesses of the forecast modeling systems, including the hydrological impacts. The usefulness of having different weather forecast operational chains cha acterized by different numerical weather prediction models and/or different model set up or initial conditions is finally shown for one of the events (IOP19).