The atmospheric water balance and precipitation regime of a moving cyclone are described. The coordinate system chosen is one that moves with the traveling storm system. The computation of the atmospheric water balance is done to yield the parameter precipitation minus evaporation as a residual. Good agreement is found between the water balance result and gauge data for three twelve-hour periods. A technique, based on the conservation of equivalent potential temperature, to determine the flow of mass and moisture within the storm system is described. The results show that the cyclone studied changed in structure from a statically unstable to a stable system over 36 hours. The distribution of rate of condensation as a function of cloud temperature is determined and a distinct change in character of this parameter is noted as the storm structure is altered.