An Operational Model for Forecasting Probability of Precipitation—PEATMOS PoP

Abstract

A dynamical-statistical model for use in probability of precipitation forecasting out to 60 h is described. This model has been fully operational twice daily in the National Weather Service (NWS) since January 1972. The acronym for the model is PEATMOS PoP, for Primitive Equation And Trajectory Model Output Statistics, Probability of Precipitation. All inputs to the PoP model are provided at the National Meteorological Center by the normal outputs of the Primitive Equation and Trajectory models. We have continued to modify and adjust the model in the various ways described in order to improve its performance. An evaluation of performance shows that the accuracy of the forecasts produced by this model has continued to increase from year to year. PoP forecasts going to the public from NWS local offices have also improved with time. This improvement is likely the result of better guidance (PEATMOS PoP), although there was a slight adjustment period that lasted only a few months when the objective guidance was introduced.