Momentum, moisture and heat budgets of a convective system over the Julian Alps on 4 october 1999 during MAP IOP05

One of the objectives of MAP aimed at a better understanding of mechanisms of creation or enhancement of precipitation by special configurations of topography in complex terrain. During IOP05, on 4 October 1999, the US National Center for Atmospheric Research and the National Oceanic and Atmospheric Administration P3 aircraft carrying meteorological Doppler radars and other instruments have been used to investigate the dynamic, thermodynamic and microphysical properties of a convective system. This one occurred near the border between Italy and Slovenia in a transition region between the flat Adriatic coast and the Julian Alps. It was within range of the operational Italian Doppler radar at Fossalon Di Grado, from its early stage to its dissipation. This precipitating system started on the Italian side, as a warm and moist southwesterly flow impinged on the southward slopes of the Alps. It moved eastwards, and reached its mature stage around 0800UTC, as a 150 km long and 10-20 km wide line of very intense convective cells. After 0900UTC, a region of stratiform precipitation developed on its northern side. The system dissipated by about 1200UTC as it moved toward Croatia. In both convective and stratiform regions, radar observations and numerical modeling suggested strong influence of the underlying topography. Momentum, heat and moisture budgets are deduced from both the radar observations and the numerical results. They will be discussed in relation with the evolution of the precipitating system and its interaction with the underlying terrain.