The most important parameters determining the nature of flow past mesoscale orography are the Froude number, F=U/NH, and the Rossby number, R=U/fL, where U is the mean flow speed, N is the buoyancy frequency of the atmosphere, f is the Coriolis parameter, and L and H are the horizontal and vertical scales of the orography, respectively. The regime where the Froude number is small is of particular interest because it is geophysically relevant to flow past the larger mountain ranges and because no analytical solution exists which can describe this regime. Here I present some new solutions which describe the flow in this regime. The new feature of this approach is to recognise the nature of the flow asymmetry associated with the Coriolis acceleration. This assymetry is subtly different from the familiar result from quasi-geostrophic theory (which is valid only when the Rossby number is much smaller than the Froude number).
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12th Conference on Atmospheric and Oceanic Fluid Dynamics