1 Creation , Evaluation and Implementation of a Precipitation - Type Forecasting System

This COMET proposal describes a two-year project, beginning on 6/1/00, that will create, evaluate, and implement the first precipitation-type probabilistic forecast system, using ensemble forecasting and consensus forecasting concepts, at the Hydrometeorological Prediction Center (HPC) and the Storm Prediction Center (SPC). The research component of this project will evaluate the quality of various precipitation-type algorithms and investigate various ensemble forecasting concepts in applying the collection of algorithms. The operational component of the project will create probabilistic forecasts of each precipitation type diagnosed by the algorithms and consensus forecasts of the most probable precipitation type. After sufficient development and testing at the HPC and the SPC, these forecasts will be made available routinely to all National Weather Service (NWS) offices within two years, provided approval is granted by the NWS. I. Overview Precipitation-type forecasting remains a difficult task for even the most experienced forecasters because of the uncertainties associated with forecasting the evolution of winter weather systems that produce snow, rain, ice pellets, and freezing rain, as well as inadequate atmospheric data sampling, a complete knowledge of precipitation microphysics, and limited techniques to evaluate high resolution model data. The importance of forecasting these events accurately is illustrated by a set of statistics compiled the Office of Meteorology, which reports