|One final upgrade is planned for the current version of the North American Mesoscale (NAM) Forecast System|
- Changes in the grid spacing of the CONUS NAM nest from 4 to 3 km, Alaska nest from 6 to 3 km, and CONUS fire-weather nest from 1.333 to 1.5 km. Yes, the latter is a decrease in resolution, but probably not significant.
- More frequent calls of some model physics packages to every 2nd time step and more frequent radiation calls for the NAM 12-km domain
- Specific humidity advection now done every time step (shockingly, this wasn't already being done)
- Changes to the model convective parameterization in the 12-km domain
- Updated cloud microphysics
- Land-surface model improvements
- Completely updated data assimilation system
- Use of a new climatology of fresh water lake temperature for inland water bodies not resolved by the current 1/12th degree analysis
- Reduced terrain smoothing in NAM nests
Gory details available from Technical Implementation Notice 16-41, available here, and the poster below.
It is anticipated that this will be the final upgrade to the NAM and that eventually a new cloud-allowing modeling system will be developed using the Geophysical Fluid Dynamics Laboratory (GFDL) Finite-Volume Cubed-Sphere Dynamical Core (FV3), which was recently chosen for NOAA's next-generation global environmental modeling system and replacement for the GFS.