The eddies are loosely defined as coherent patterns of flow velocity, vorticity and pressure. Vortex stretching is associated with a particular term in the vorticity equation. These are; Coriolis vorticity, curvature vorticity, and shear vorticity. Instability is caused when the vortex tube, the line of concentrated vorticity, is displaced. CVA produces divergence as a result of how there is a loss of cyclonic vorticity. Further simplification, by removing terms describing vorticity yields the full potential equations. The vorticity and inertia of rip currents have been studied. This flow is accounted for by the diffusion term in the vorticity transport equation. Potential vorticity (PV) is seen as one of the important theoretical successes of modern meteorology. This reduces the radial length scale of the associated vorticity. The conserved quantity in equation (3) is later called the "shallow water potential vorticity". Helicity is vorticity in motion along a third axis in a corkscrew fashion. Thus in irrotational flow the vorticity is zero. The upstream flow is uniform and has no vorticity. Fluid elements initially free of vorticity remain free of vorticity.