Détermination des paramètres météo nécessaires à la prévision du risque d'avalanche à échéance d'un jour

Météo-France : CNRM/CEN

Abstract

The avalanche hazard estimation for the present and the coming days is one of the main tasks of the avalanche forecaster. For four years, some of them, in the alpine massifs of France, have been using a serie of automatic numerical models. These programs describe in real time the main meteorological conditions (Safran), the evolution of the snow cover (Crocus) and the resulting avalanche risks (Mepra) at different elevations, slopes and aspects of the considered massifs.

This paper presents the latest evolution of this automatic tool. This new version now makes it possible to provide one-day forecast states of snow cover over both the Alps and Pyrenees massifs including the main characteristics of the snowpack and an assessment of the corresponding avalanche hazards.

To achieve this result, the main changes concerned Safran. Two combined methods are used inside the same package: adaptations of larger scale meteorological forecasts and use of observations of analogous weather situations of the past. These two approaches are complementary especially for the evaluation of precipitation where the second solution has important fine scale information while the first exhibits important local biases. Validation of this new application was carefully done and proved the quality of the method, now used in real time by local forecasters.