My choice of atmospheric model is SPEEDY which is a general circulation model of the atmosphere.  It has a simplified parametrization and primitive equation dynamics.  And there are five prognostic variables of U, V, T, q, Ps.  This models is spectral model with T30 resolution which corresponds to 96X48 horizontally.  And it has only seven vertical layers which is quite coarse compared to the operational model.  Finally, the current version of SPEEDY which IÕm using has 6-hour forecast.