With the objective characterizing atmospheric dynamics for particular months, structures appearing at large scales on Meteosat water vapor images are tracked with similar methods as those used for cloud tracking in other channels at smaller scales. For this purpose sampled ISCCP images at resolution 30 km with time intervals of 3 hours are used. Mean monthly ``motion fields'' are computed. These fields are very consistent with the general circulation of the upper troposphere. They are shown to represent the motions of synoptic systems rather than the wind at a particular level. Nevertheless, significant interannual variations of the large scale circulations can be observed.