The Weather Prediction Center Day 8-10 Forecast Experiment: Development and Utilization of Forecast Tools

The Weather Prediction Center (WPC) and the National Weather Service (NWS) currently provide detailed weather forecasts out to day 7. There is intense demand and interest in extending daily weather forecasts to ten days. Extending daily forecasts out to ten days requires the development of a methodology to turn raw model guidance into consistent, actionable products and services for decision makers. To accomplish this, WPC’s Hydrometeorological Testbed (HMT) began a real-time experiment dedicated to forecasting for days 8, 9, and 10. Forecasting at these lead times requires the heavy use of ensemble forecasts. Accordingly, forecasts tools that mine the ensemble data to extract meaningful signals about sensible weather for days 8, 9, and 10 are of high value. This presentation will serve as an overview of some of the tools that have been developed and utilized to assist in the preparation of forecasts made during this experiment.

Focus will be paid to an ensemble clustering tool under development. The tool is an application of fuzzy clustering where ensemble members from the Global Ensemble Forecast System (GEFS), the Canadian Global Ensemble Prediction Systems (GEPS), and the European Center for Medium Range Weather Forecasts Ensemble Prediction System (ENS) are clustered based on their mean 500-hPa height pattern for days 8-10. A forecaster can view these clusters and each cluster’s forecast for sensible weather elements to get a better idea of the potential forecast scenarios for days 8, 9, and 10. This is more instructive than viewing the ensemble mean forecast from each ensemble prediction system (EPS). In addition, the tool has shown great potential as a way to create more tailored forecasts for days 8, 9, and 10 than a forecast created by blending ensemble means from each EPS.