Initiation of convection over the Black Forest mountains during COPS IOP15a

Doppler-On-Wheels radar observations made during the Convective and Orographically-induced Precipitation Study (COPS) on 12 August 2007 showed that precipitating clouds only developed between the north-south orientated Murg and Nagold Valleys of the northern Black Forest. The clouds produced moderate precipitation. The Weather Research and Forecasting (WRF) model run at 700 m horizontal resolution in the inner domain was able to simulate the location of the precipitation. Insight is therefore gained into the physical mechanisms responsible for the initiation and development of the convection. Convergence lines resulting from thermally driven flows constrained the initial location of the convection within warm and moist cores produced by heating on elevated surfaces. The heaviest precipitation was later produced by secondary convection, which was initiated within the cores at the boundary between cold-pool outflows and thermal flows.