Embedded Files
The technical name of this model is the NAM-NMM, but the name North American Model (NAM) is given to whichever model serves as the primary operational forecasting model for the United States. This model is under active development and is therefore frequently being improved. The model uses a limited-area domain, centered over North America and including much of the surrounding oceans. It has the finest horizontal resolution and nearly the highest vertical resolution (4 layers shy of the GFS) of all the models currently in use at NCEP, and thus has the potential of forecasting the weather with the greatest accuracy. However, it is also the newest model, and is therefore not as sophisticated in some aspects as the other models (for instance its model output statistics may not be the most accurate since it has been operating for the least amount of time).
Like most current models, this model uses a hybrid sigma-pressure height coordinate, with sigma coordinates near the surface transitioning to pressure coordinates aloft. The primary difference between this model and other models is that this model is non-hydrostatic, which means that it processes vertical motions in the atmosphere explicitly rather than relying upon the hydrostatic approximation (which you may recall from the lesson on Air Pressure, Temperature, and Height).
The NAM is run four times a day, at 00Z, 06Z, 12Z, and 18Z. The horizontal resolution is 12 km and there are 60 vertical levels. This is the highest resolution model in the NMC suite of models. In principle, this should allow it to perform best when dealing with topographic effects, when resolving the shape and size of mountain ranges is critical for forecasting their impact.
Report abuse