WRF model simulations of a quasi-stationary, extreme–rain–producing mesoscale convective system

On 6-7 May 2000, an area of deep convection produced extreme rainfall amounts (in excess of 300 mm) and flash flooding over eastern Missouri. Forecasts from the Weather Research and Forecasting (WRF) model will be presented that are quite accurate in their representation of the back-building, quasi-stationary nature of the convection in this event.

When initialized with 40-km data from the Eta model and run with grid spacing on the order of 1 km, the model produces a backbuilding, very slow-moving area of convection with heavy rainfall. The evolution of the convective system will be examined, with an analysis of the growth and decay of the individual convective cells that comprised the simulated convective system. In addition, the forcings responsible for the maintenance of the convection will be discussed, which include the development of only a very weak cold pool and the presence of a mesoscale convective vortex.

The ability of the WRF model to reproduce these typically difficult-to-forecast structures using a configuration suitable for real-time operations is promising. These results suggest that there may be potential for increased understanding and, in some cases, improvements in prediction of the convection that produces extreme precipitation and resultant flash flooding.