The multiplicative broken-line model is proposed as a generalization of the discrete multiplicative cascade to generate time series of mean areal rainfall during a storm. The main advantage of the new model is the ability to specify an outer scale for the cascade which is less than the duration of the event and an arbitrary branching number. Model parameters are estimated for time series of 10 min mean areal rainfall over squares with 16 and 128 km sides. The model output is compared with the measured data and is found to be able to reproduce the power, spectra, correlation functions, and probability distributions of the time series at both scales. ¿ 2000 American Geophysical Union