A High-Resolution Numerical Weather Prediction Model for Nowcasting Precipitation in the Grand-Duchy of Luxembourg (NWPLux)

Compared to alluvial floods, flash or pluvial floods are difficult to predict because they result from intense and brief periods of extreme precipitation. The project NWPLux aims to develop, a high-resolution numerical weather prediction (NWP) model for effective local heavy rainfall prediction in a nowcasting scenario and provide real time for flood simulation. Modelling is based on the Weather Research and Forecasting (WRF) model, with a large-eddy simulation (LES) type 3-dimensional cloud model to simulate small-scale, high-intensity convective precipitation. It is the first such dedicated NWP model for Luxembourg and the Greater Region. As part of this project, we will also test run the LISFlood flood model in an operational inundation forecast mode, meaning that the flood model will be run with the WRF precipitation forecasts as inputs.
As an initial run the WRF model was setup with two distinct domains, specifically the Greater Region and Luxembourg with respective horizontal grid spacing of 16 km and 4 km, leveraging high resolution static data. Met data from the NCAR RDA dataset ds083.2 was utilized, spanning from July 08, 2021 to July 15, 2021, and was subjected to the "Conus" physics suit. The output interval was one hour.
Preliminary results from NWP runs indicated that the higher resolution simulations (4 km) exhibited superior performance when compared to the lower resolution simulations (16 km).

Keywords: NWP, WRF, Flash flood, LISFlood, cloud modelling