A note on the properties of the primitive hydrostatic equations of motion

Discussion of the proper boundary conditions to use in limited area forecasting models requires knowledge of the properties of the governing equations. the theory of Oliger and Sundstrom states that the primitive hydrostatic equations commonly used are not hyperbolic and no local boundary conditions can be chosen. This paper shows their result to be incorrect, the equations are hyperbolic but not all the characteristics involve the time variable. Implications for the boundary conditions are discussed.