The concept of Isentropic Potential Vorticity in rotating planar fluids is shown to be a special case of a physical system with a divergence free, hence conserved, Topological Torsion 3-form. The physical system is presumed to be described by a 1-form of Action, and the evolutionary process is presumed to be described by a singly parameterized contravariant vector field. The induced differential 1-form of Work is constrained such that its Pfaff dimension is 2. The resulting dynamics is thermodynamically reversible. The methods have application to weather forcasting and do not require that the evolution of the rotating compressible fluid be isentropic.

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