Résumé
With the computing power it brings, the new generation of massively parallel computers allows one to perform a "seamless" modeling of weather on large grids, but it requires a large parallel computing capability for the models. Due to improvements in this direction in the meteorological model of the French research community MESO-NH, a computing performance of over 4 Teraflop/s was obtained with 130000 cores on the machine of the European computer center PRACE. This is a first in France for a weather code. A high resolution simulation, covering the Atlantic and Europe, of the tropical cyclone Helene and its interaction with a planetary wave was also conducted, for which the excellent result gives hope to an improved weather forecasting in Europe.