We focus on the Probable Maximum Precipitation (PMP) in the Upper Tone River basin, through weather conditions change. In order to evaluate total amount and distributions of heavy rainfalls, WRF model is used. The results are summarized as follows: (1) The increase of relative humidity in the atmosphere affects not only total rainfall but also its temporal variation and it also makes peak time earlier. Moreover it may generate a first peak before main peak rainfall, which will affect the initial loss of rainfall and increase maximum discharge. (2) The increase of wind speed affects not only total rainfall but also spatial distribution of rainfall. (3) Moisture fluxes show high correlation with total rainfall through grid point value (GPV) data from meso-scale objective analysis and WRF model calculation in the upper Tone River Basin, which clearly suggests they can be used as a suitable parameter to estimate PMP.
