4A.5 Upgrade of NCEP Global Ensemble Forecast System

Monday, 1 June 2009: 5:00 PM
Grand Ballroom East (DoubleTree Hotel & EMC - Downtown, Omaha)
Yuejian Zhu, NOAA/NWS/NCEP/EMC, Camp Springs, MD; and Z. Toth, R. Wobus, D. Hou, and B. Cui

New NCEP Global Ensemble Forecast System (GEFS) has been planned to implement in 2009. This implementation will expect to improve NCEP GEFS model forecasts and the quality of NAEFS (The North American Ensemble Forecast System) products. The NAEFS is operationally joined multi-model ensemble forecast system since 2006, which combined NCEP and CMC's ensemble forecasts after post process, such as bias correction and downscaling. This upgrade mainly includes following changes: 1). Increasing horizontal resolution from T126 to T190 out to 384 hours. Increasing model resolution will expect to have better forecasts for first 3-5 days. 2). Using 8th order horizontal diffusion instead of 4th order of current operation. Experiments demonstrated the higher order diffusion will promise better ensemble forecast and ensemble spread which allows waves interaction and propagation in reality. 3). Adding stochastic perturbation scheme to account for random model errors. This process will increase ensemble spread and reduce RMS errors, especially for longer forecast. Overall, NCEP new GEFS will enhance our model forecasts and NAEFS products significantly according to two 2-month retrospective experiments which are November-December 2007, and August-September 2008.
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