Experimental point and area precipitation probability forecasts for a forecast area with significant local effects

Abstract This paper describes the results of a recent experiment designed to investigate the ability of forecasters to make point and area precipitation probability forecasts. The location of the experiment (Rapid City, South Dakota) was chosen because of the existence of a network of raingages and because of significant local effects that cause variation among points in terms of precipitation occurrence. A similar experiment conducted at a different location in 1972–73 yielded encouraging results (see Winkler and Murphy, 1976), but the lack of variability in precipitation occurrence among points in the forecast area in that experiment made it difficult to answer several important questions of interest. On each forecasting occasion during the Rapid City experiment, the forecasters made an average point probability forecast for the area, individual point probability forecasts for four specific points in the area, an area probability forecast, and an expected areal coverage forecast. The results indicate th...