Introduction to Next NCEP Global Ensemble Forecast System (GEFS)

The next NCEP Global Ensemble Forecast System (GEFS) is going to be a major upgrade in later 2018/early 2019 toward NCEP unified model system through Next Generation Global Prediction System (NGGPS) project. The upgrade will include:  1) Increasing model resolution and ensemble members; 2) Introducing stochastic schemes (SKEB, SPPT and SHUM) to replace current operational STTP scheme in additional to state-of-art initial analyses and perturbations from hybrid analysis and latest generation of EnKF; 3) An coupling GEFS to cover sub-season and monthly forecast from current 16 days forecast. The new GEFS will use Global Spectrum Model (GSM) on NOAA Environmental Modeling System (NEMS) that is the common modeling framework. In order to improve probabilistic forecast guidance and forecast reliability, the next GEFS upgrade will generate 20 years (1999 – 2018) reforecasts before system upgrade.

In this presentation, the improvement of probabilistic weather forecast from retrospective experiments through various upgrades will be presented in terms of verification statistics. The user concerns for current GEFS (and others) will be addressed as well. Mainly the investigation of GEFS sub-season forecast skills, from the experiments of different SST forcing to couple with ocean and sea-ice model, will be demonstrated through sub-seasonal verification matrix, such as MJO prediction, CONUS precipitation and temperature forecast, and et al.