Challenges for a new 1km non-hydrostatic model over the Alpine area

The Swiss Meteorological Office is planning to run the COSMO model with a 1 km mesh-size on an operational basis. To attain this goal the actual dynamical core of the model must be made numerically stable for an increased steepness of the orography. Moreover is should provide accurate forecasts with a minimally filtered orography. The right balance between filtering and using horizontal (numerical) diffusion needs to be found. We will show the general setup of the model and to some extent how much can be exploited from the increased horizontal (and vertical) resolution. This means also using adapted external parameters and better lower boundary conditions (soil, etc.).