Are the 3 km and the 12 km NAM the same model with different resolutions? Because they can be quite different.

[Ed, snow and hurricane fan]

I am trying to see if the 12km NAM and 3 km NAM run the same physics.  I remember the ARW, NMM and such, even if I had no clue what the differences are.

 

The 12Z 3 km and 12 km NAMs are more different for tomorrow's DFW winter event than I'd expect just from finer resolution.

[dtk]

45 minutes ago, Ed, snow and hurricane fan said:

I am trying to see if the 12km NAM and 3 km NAM run the same physics.  I remember the ARW, NMM and such, even if I had no clue what the differences are.

 

The 12Z 3 km and 12 km NAMs are more different for tomorrow's DFW winter event than I'd expect just from finer resolution.

Generally same physics with some specific (and relevant) exceptions.  See here: https://www.emc.ncep.noaa.gov/emc/pages/numerical_forecast_systems/nam.php:

The NAM nests run with the same physics suite as the NAM 12 km parent domain with the following exceptions:

• The nests are not run with parameterized convection
• The nests do not run with gravity wave drag/mountain blocking
• In the Ferrier-Algo microphysics, the 12 km domain's threshold RH for the onset of condensation is 98%, for the nests it is 100%
• The NAM nests use a higher divergence damping coefficient.
• The NAM nests advect each individual microphysics species separately; the NAM 12 km parent domain advects total condensate