1. Higher Resolution Operational Models

2. Major U.S. High-Resolution Mesoscale Models (all non-hydrostatic ) WRF-ARW (developed at NCAR) NMM-B (developed at NCEP Environmental Modeling Center) COAMPS (U.S. Navy) MM5 (NCAR, old, replaced by WRF) RAMS (Regional Atmospheric Modeling System, Colorado State) ARPS (Advanced Regional Prediction System): Oklahoma

3. Operational Mesoscale Model History in US Early: LFM, NGM (history) Eta (mainly history) MM5: Still used by some, but mainly phased out NMM- Main NWS mesoscale model, updated Eta model. Sometimes called WRF-NMM and NAM. WRF-ARW: Heavily used by research and some operational communities. NMM replaced by NMM-B

4. WRF and NMM

5. History of WRF model An attempt to create a national mesoscale prediction system to be used by both operational and research communities. A new, state-of-the-art model that has good conservation characteristics (e.g., conservation of mass) and good numerics (so not too much numerical diffusion) A model that could parallelize well on many processors and easy to modify. Plug-compatible physics to foster improvements in model physics. Designed for grid spacings of 1-10 km

6. WRF Modeling System Obs Data, Analyses Post Processors, Verification WRF Software Infrastructure Dynamic Cores Mass Core NMM Core … Standard Physics Interface Physics Packages Static Initialization 3DVAR Data Assimilation

7. Two WRF Cores ARW (Advanced Research WRF) developed at NCAR Non-hydrostatic Numerical Model (NMM) Core developed at NCEP Both work under the WRF IO Infrastructure NMM ARW

8. The NCAR ARW Core Model: (See: www.wrf-model.org)  Terrain following vertical coordinate  two-way nesting, any ratio  Conserves mass, entropy and scalars using up to 6 th order spatial differencing equ for fluxes. Very good numerics, less implicit smoothing in numerics.  NCAR physics package ( converted from MM5 and Eta ), NOAH unified land-surface model, NCEP physics adapted too

9. NWS NMM 1 —The NAM RUN Run every six hours over N. American and adjacent ocean Run to 84 hours at 12-km grid spacing. Uses the Grid-Point Statistical Interpolation (GSI) data assimilation system (3DVAR) Start with GDAS (GFS analysis) as initial first guess at t-12 hour (the start of the analysis cycle) Runs an intermittent data assimilation cycle every three hours until the initialization time. 1-Non-hydrostatic mesoscale model, NAM: North American Mesoscale run

11. NMM-B Hybrid sigma-pressure vertical coordinate 60 levels Betts-Miller-Janjic convective parameterization scheme Mellor-Yamada-Janji boundary layer scheme

12. NMM-B Details One-way nested forecasts computed concurrently with the 12-km NMM-B parent run for –CONUS (4 km to 60 hours) –Alaska (6 km to 60 hours) –Hawaii (3 km to 60 hours) –Puerto Rico (3 km to 60 hours) –For fire weather, moveable 1.33-km CONUS and 1.5-km Alaska nests are also run concurrently (to 36 hours). A change in horizontal grid from Arakawa-E to Arakawa- B grid, which speeds up computations without degrading the forecast

13. 13 September 2011 NAM-B Upgrade New NAM NEMS based NMMB B-grid replaces E-grid Parent remains 12 km to 84 hr Four Fixed Nests Run to 60 hr –4 km CONUS nest –6 km Alaska nest –3 km HI & PR nests Single placeable 1.33km or 1.5 km FireWeather/IMET/DHS run to 36hrSingle placeable 1.33km or 1.5 km FireWeather/IMET/DHS run to 36hr

14. NMMB 4-km Conus

15. NAM Generally less skillful than GFS, even over U.S. Generally inferior to WRF-ARW at same resolution (more diffusion and smoothing, worse numerics)

16. Navy COAMPS (Coupled Ocean/Atmosphere Mesoscale Prediction System) Sigma-Z Atmosphere And Ocean