Simulated stratification for prediction of precipitation type

The updating of MOS forecasts of the probability of precipitation type (freezing, frozen, or liquid) with a recent observation constitutes an example in using indicator variables to simulate stratification of the developmental sample. In this example, inclusion of the observation in a primitive manner in the updating regression equations does not make full use of the new information. It is proposed that simulated stratification is useful for updating guidance forecasts, such as MOS, for projections of a few hours, and that the simulation may be easier from both developmental and operational aspects than actually stratifying the sample and producing regression relationships for each stratum.