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This paper presents RISKMED, a project targeted to create an Early Warning System (EWS) in case of severe or extreme weather events in the central and eastern Mediterranean and specifically in southern Italy, northwestern Greece, Malta and Cyprus. As severe or extreme weather events are considered, cases when the values of some meteorological parameters (temperature, wind, precipitation) exceed certain thresholds, and/or a severe weather phenomenon (thunderstorm, snowfall) occurs. For an accurate weather forecast, selected meteorological models have been operated daily, based on a nesting strategy using two or three domains, providing detailed forecasts over the above mentioned areas. The forecast results are further exploited for the evaluation and prediction of human discomfort and fire weather indices. Finally, sea wave models have also been operating daily over the central and eastern Mediterranean Sea. In case a severe or extreme weather event is forecasted within the next 48 or 72 h for selected target areas (sub-regions defined by their morphological and population characteristics), the local authorities and the public are informed via a user-friendly graphic system, the so-called RISK MAP. On the web page of the Project (http://www.riskmed.net), additional information is provided about the real-time values of some meteorological parameters, the latest satellite picture and the time and space distribution of lightning during the last 24 h. The RISKMED project was financed by the EU and the Ministries of National Economy of Greece, Italy, Malta and Cyprus, in the frame of INTERREG IIIB/ARCHIMED programme. [ABSTRACT FROM AUTHOR]

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 northeasterly barrier-type wind south of the Alps, and was responsible for precipitation exceeding 320mm in less than 12 h, 240mm 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. [ABSTRACT FROM AUTHOR]

A forecasting system has been implemented for operational weather prediction over southern Italy in the framework of the RISKMED (INTERREG IIIB) project, which aims at weather-risk reduction in the central and eastern Mediterranean area. The system comprises two different regional forecasting chains, one based on BOLAM and MOLOCH models, the second based on the Weather Research and Forecasting (WRF) model. On 26 September 2006, a subsynoptic-scale vortex developed over the Mediterranean Sea and affected south-eastern Italy. The cyclone was documented by radar reflectivity maps, Meteosat Second Generation satellite images and surface stations data. The observational analysis showed that the cyclone possessed the typical characteristics of a Mediterranean tropical-like cyclone. All the limited-area models employed in RISKMED were able to properly forecast the formation of the small-scale vortex, although with differences in intensity, trajectory and evolution. The predictability of the event has been evaluated employing a multi-model, multi-analysis approach. The simulation results show strong sensitivity to the specification of the initial and boundary conditions. Sensitivity experiments were performed in order to analyse the mechanisms responsible for the development and the maintenance of the cyclone over the sea. The life cycle of the vortex turned out to be characterized by different phases: the orographic cyclogenesis on the lee side of the Atlas Mountains; the initial phase of development, characterised by the critical role played by the surface heat fluxes; the transition to a tropical-like cyclone mainly as a consequence of the latent-heat release associated with strong convective activity over the Ionian Sea; finally, the maintenance of the vortex strength due to both the surface fluxes and the release of latent heat. [ABSTRACT FROM AUTHOR]

In the field of hydrological prediction for medium-sized watersheds, characterized by complex orography and short response times, forecasts cannot rely only upon observed precipitation: predicted rainfall is in this case an essential input for hydrological models. However, the quality and reliability of deterministic numerical precipitation forecasts driving a hydrological model are often unsatisfactory, because uncertainty in Quantitative Precipitation Forecasts (QPFs) is considerable at the scales of interest for hydrological purposes. The uncertainty inherent in precipitation forecast can be accounted for better estimating the uncertainty associated with the flood forecast, in order to provide a more informative hydrological prediction. The methodology proposed and adopted in this work is based on a hydrological ensemble forecasting approach that uses multiple precipitation scenarios provided by different high-resolution numerical weather prediction models, driving the same hydrological model. In this way, the uncertainty associated with the meteorological forecasts can propagate into the hydrological models and be used in warnings and decision making procedures relying upon a probabilistic approach. In the framework of RISK AWARE, an INTERREG III B EU project, a detailed analysis of two cases of intense precipitation affecting the Reno river basin, a medium-sized catchment in northern Italy, has been performed. One case study has been performed using lateral boundary values derived from analysed fields, the other simulating a real time forecast, i.e., using forecasted boundary conditions. Four different meteorological models (Lokal Modell, RAMS, BOLAM and MOLOCH), operating at different horizontal resolutions, provide QPFs which are used to force the hydrological model. The discharge predictions are obtained by means of the physically based rainfall-runoff model TOPKAPI. The results provide examples of the uncertainties inherent in the QPF and show that the hydrological response of the Reno river basin, as simulated by the TOPKAPI model, is highly sensitive to the correct space-time localization of precipitation, even if the total amount of rainfall is, on average, well forecasted. The system seems able to provide useful information concerning the discharge peaks (amount and timing) for warning purposes. [ABSTRACT FROM AUTHOR]

Within the framework of the European Interreg IIIb Medocc program, the HYDROPTIMET project aims at the optimization of the hydrometeorological forecasting tools in the context of intense precipitation within complex topography. Therefore, some meteorological forecast models and hydrological models were tested on four Mediterranean flash-flood events. One of them occurred in France where the South-eastern ridge of the French "Massif Central", the Gard region, experienced a devastating flood on 8 and 9 September 2002. 24 people were killed during this event and the economic damage was estimated at 1.2 billion euros. To built the next generation of the hydrometeorological forecasting chain that will be able to capture such localized and fast events and the resulting discharges, the forecasted rain fields might be improved to be relevant for hydrological purposes. In such context, this paper presents the results of the evaluation methodology proposed by Yates et al. (2005) that highlights the relevant hydrological scales of a simulated rain field. Simulated rain fields of 7 meteorological model runs concerning with the French event are therefore evaluated for different accumulation times. The dynamics of these models are either based on non-hydrostatic or hydrostatic equation systems. Moreover, these models were run under different configurations (resolution, initial conditions). The classical score analysis and the areal evaluation of the simulated rain fields are then performed in order to put forward the main simulation characteristics that improve the quantitative precipitation forecast. The conclusions draw some recommendations on the value of the quantitative precipitation forecasts and way to use it for quantitative discharge forecasts within mountainous areas. [ABSTRACT FROM AUTHOR]

A nudging procedure for the assimilation of rainfall data into a mesoscale model [the Bologna Limited Area Model (BOLAM)] has been developed in order to improve short-range forecasting. The scheme modifies the model specific humidity profiles at every time step, according to the difference between observed and forecast precipitation. Different relaxation procedures are applied depending on the precipitation type (large-scale or convective rain), as estimated by the model itself. Optimizations of the nudging parameters and assessment of the scheme's performance was carried out in an idealized framework [(Observing System Simulation Experiment) OSSE-type strategy], implementing a lagged forecast scheme. Two events were selected for this purpose, both characterized by heavy precipitation in the Mediterranean Basin. The first was a severe orographic rainfall event, associated with the passage of a frontal system over the Alps during the Mesoscale Alpine Programme (MAP) field phase, in September 1999. The second was characterized by the development of a very deep low close to the Algerian coast, where heavy precipitation caused a disastrous flood in the city of Algiers in November 2001. The effects of rainfall assimilation were evaluated, both qualitatively and quantitatively, in terms of precipitation forecasts and modification of dynamical fields, with particular attention to the impact on cyclone development. Finally, sensitivity tests were performed in order to assess the dependence of the nudging procedure on rainfall data characteristics (length of the accumulation period and associated error) and model error. [ABSTRACT FROM AUTHOR]