Abstract : 3N.8
Foehn Verification with the 'aLMo' Model

Klaus Burri, Bruno Dürr, Patrick Hächler, Thomas Gutermann, Alfred Neururer, Richard Werner, Uwe Schickedanz
AGF, Working Group Foehn-Research Rhine Valley/Lake Constance

The "Working Group Foehn-Research Rhine Valley/Lake Constance" (AGF, Arbeitsgemeinschaft Föhnforschung Rheintal/Bodensee) is measuring the meteorological parameters and investigating foehn phenomena in the Rhine valley since the early 1970's. Their main task is to find plausible criteria for a reliable foehn forecast.

To forecast foehn is a difficult task, especially in the upper Rhine Valley with its complex topography. Existing forecast models are able to predict winds quite well in middle and higher altitudes; but most of them fail in forewarning foehn in the ground layer which is of most interest in order to warn the population of severe foehn storms.

MeteoSwiss and several other institutions in Europe developed and improved the model 'aLMo' (alpine model, originally based on DWD's «local model») over the last years. It shows southerly winds above the boundary layer quite well, but beginnings and endings of a foehn phase in the ground layer are still predicted very vaguely. On the other hand it is necessary to forecast them precisely in order to install a reliable gale warning, i.e. a foehn warning.

The AGF is going to show with some case studies strengths and weaknesses of 'aLMo' in forecasting foehn in the upper Rhine Valley compared to some cases in the Reuss and Linth Valley.