Populated coastal regions in the Mediterranean are known to be severely affected by extreme weather events that are initiated over maritime regions. These weather events are known to pose a serious problem in terms of numerical predictability. Different Data Assimilation techniques are used in this study with the main aim of enhancing short-range forecasts of two challenging severe weather events.

Forecasting precipitation over the Mediterranean basin is still a challenge. In this context, data assimilation techniques play a key role in improving the initial conditions and consequently the timing and position of the precipitation forecast. For the first time, the ability of a cycling 4D-Var to reproduce a heavy rain event in central Italy, as well as to provide a comparison with the largely used cycling 3D-Var, is evaluated in this study.

Floods and severe rainfall are among the major natural hazards in the Mediterranean basin. Though precipitation weather forecasts have improved considerably, precipitation estimation is still affected by errors that can deteriorate the hydrological forecast. To improve hydrological forecasting, a regional-scale meteorological–hydrological ensemble is presented. This allows for predicting potential severe events days in advance and for characterizing the uncertainty of the hydrological forecast.

This work explores the potentialities in urban hailstorms detection of X-band miniradar measurements. The results show that the latter are suitable for early monitoring of hail events at urban scale, especially when combined with conventional meteorological data. The experimental hail detection product developed in this study, although trained for a specific urban environment (i.e. Naples urban area), can be easily adapted to other areas where detailed meteorological information is needed.