Climate-Biased Storm-Frequency Estimation

Storm frequencies for the future are often estimated directly from past historical records of sufficient length. The estimation requires no detailed knowledge of the areaʹs meteorology, but presumes it is unchanged in the future. However, the climate seldom remains static. Numerous climate forecasts of meteorological probabilities over extended periods are now available. It is possible to use these meteorological forecasts directly in the estimation of storm frequencies from the historical record. A heuristic approach is defined here to estimate storm frequencies that recognize forecasts of extended weather probabilities. Basically, those groups of historical meteorological record segments matching forecast meteorological probabilities are weighted more than others, during the estimation of storm frequencies. (Affiliated groups of hydrologic record segments may be similarly weighted for hydrological estimation; e.g., flood frequency estimation.) An example of frequency estimation is made for maximum annual daily flow, using currently available agency meteorological forecasts in the United States and Canada.