1. 1 Global Ensemble Strategy Presented By: Yuejian Zhu (NWS/NCEP) Contributors: EMC staff

2. 2 Operational System Attribute(s) System NameAcronymAreal Coverage Horz Res Cycle Freq Fcst Length (hr) Global Ensemble Forecast SystemGEFSGlobal34km/ 52km 6hrs384hrs North American Ensemble Forecast System (NCEP+CMC) NAEFSGlobal50km12hrs384hrs National Unified Operational Prediction Capability (NCEP+CMC+FNMOC) NUOPCGlobal50km12hrs384hrs SystemAttributes GEFSDA:NCEP hybrid GSI/EnKF; Ini: EnKF (f06) + TS relocation + Centered all perturbed vectors; Model: GFS NAEFS (CMC)DA: 4DV; Ini: EnKF; Model: GEM – gridded model NUOPC (FNMOC)DA: 4DV; Ini: Banded ET; Model: NAVGEM – spectrum model System Data Assimilation or Initialization Technique

3. 3 Why System(s) are Operational?  Primary stakeholders and requirement drivers All NCEP service centers; NWS WFO/RFC; MDL and NWC Public and private user/sector NAEFS – MOU of US, Canada and Mexico NUOPC – MOU of NOAA and DoD (?)  What products are the models contributing to? Global products (300+ variables) at 0.5degree resolution Every 3hrs/6hrs out to 8/16 days Key products: PQPF, T2m, Wind@10m, Hurricane tracks  What product aspects are you trying to improve with your development plans? PQPF, T2m, Wind@10m (especially for CONUS and OCONUS) Hurricane track and intensity  Top 3 System Performance Strengths Ensemble mean - 500hPa height; hurricane track; T2m Probabilistic guidance – PQPF, forecast uncertainty (RMOP) Extreme weather events  Top 3 System Performance Challenges Improvement of sensible weather elements Reduce model bias Extended-range hurricane track forecasts (beyond day 5)

4. 4 System Evolution Over the Next 5 Years  Major forcing factors User requirement and seamless forecast approach Key component of WRN (weather ready nation)  Science and development priorities Represent initial (or analysis) uncertainty Near surface, land and ocean Represent model (dynamical and/or physical) uncertainty Stochastic parameterizations Add value through multi-model ensemble approach (NAEFS and NUOPC)  What are your top challenges to evolving the system(s) to meet stakeholder requirements? Resources and trade-off Tasks: seamless forecast - both of short-range and week-2 Upgrade: frequently (from WPC …) and less frequently ( from NWC …)  Potential opportunities for simplification going forward NGGPS? Unified coupled global model

5. 5 Top 3 Things You Need From the UMAC 1.Like to understand a key difference of NCEP and ECMWF global (ensemble) system development? Strategy of science and technique; Or management and user requirement; Or resource? 2.Is it important to have coupling system for short-term (or weather) forecast when we face many challenges today? If not, what our priority should be? 3.A challenge to have one global ensemble system to cover 1-30 days (short-term and extended-range) forecast. Uniform or variable resolutions? Ensemble size?

6. 6 Extra slides for reference

7. 7 NCEPCMCNAEFS ModelGFSGEMNCEP+CMC Initial uncertaintyETRETKFETR + ETKF Model uncertainty/Stochasti c Yes (Stochastic Pert)Yes (multi-physics and stochastic) Yes Tropical stormRelocationNone Daily frequency00,06,12 and 18UTC00 and 12UTC ResolutionT254L42 (d0-d8)~55km T190L42 (d8-16)~70km About 50km L72 1*1 degree ControlYes Yes (2) Ensemble members20 for each cycle 40 for each cycle Forecast length16 days (384 hours) 16 days Post-processBias correction (same bias for all members) Bias correction for each member Yes Last implementationFebruary 14 th 2012November 18 th 2014 NAEFS Current Status Updated: November 18 th 2014

8. NCEPCMCFNMOC ModelGFSGEMGlobal Spectrum Initial uncertaintyETREnKF(9) Banded ET Model uncertainty Stochastic Yes (STTP)Yes (multi-physics and Stochastic) None Tropical stormRelocationNone Daily frequency00,06,12 and 18UTC00 and 12UTC ResolutionT254L42 (d0-d8)~55km T190L42 (d8-16)~70km ~ 50km L72 T239L50 ~ 55km ControlYes Ensemble members20 for each cycle Forecast length16 days (384 hours) Post-processBias correction for ensemble mean Bias correction for each member Bias correction for member mean Last implementationFebruary 14 2012November 18 2014May 21 2014 NUOPC Current Status Updated: November 18 th 2014