Incorporating parameter dependencies into temporal downscaling of extreme rainfall using a random cascade approach

•Volume of rainfall, time of day, season, structure of event have significant effects.•An analysis of 108 years of rainfall data show weak decadal scale trends.•A 16-parameter-per-level model performs well in terms of fine scale extremes.•Empirically derived scale dependence leads to a model with only 4 parameters.•The simple model almost matches performance of the original model.