Isentropic coordinates enable extra resolution near fronts and the tropopause.
As of summer 2000, the RUC-2 has 40 vertical levels. The model's vertical layer distribution varies depending upon the weather situation. As the graphic below shows, a RUC model level may be isentropic in some horizontal areas, yet terrain-following in others. This terrain-following spacing compacts somewhat as the terrain elevation increases. Excellent resolution of the boundary layer is provided in all locations, including over higher terrain where layers tend to get compacted.