The multiplicative broken-line model is proposed as a generalization of the
discrete multiplicative cascade to generate time series of mean areal rain
fall 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 t
he 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 proba
bility distributions of the time series at both scales.