Climatological and monthly means are computed for radiosonde data at Manaus and Belém (1968-1976). Geopotencial height and wind data at upper levels show evidence of the meridional movement of a strongly divergent high pressure system associated with the area of maximum convection. At low levels, the winds, particularly at Manaus, show an annual cycle linked to the meridional displacement of the equatorial trough and its accompanying area of maximum convection (upper level high pressure system). On the average, the precipitable water (Pw) is greater at Manaus than at Belém. However, evidence is presented indicating that this is not always the case and that considerable diurnal variation in Pw exists at each station. Mean monthly vertical motions are calculated for the area within the triangle formed with Belém, Manaus and Vilhena as the vertices. These vertical motions show a strong relationship to monthly rainfall totals within the triangle indicating that interannual and monthly rainfall variations may be due to large scale atmospheric circulation changes.