  The self-organization of turbulence into regular zonal flows can be
fruitfully investigated with quasilinear methods and statistical descriptions.
A wave kinetic equation that assumes asymptotically large-scale zonal flows is
pathological. From an exact description of quasilinear dynamics emerges two
better geometrical optics approximations. These involve not only the mean flow
shear but also the second and third derivative of the mean flow. One
approximation takes the form of a new wave kinetic equation, but is only valid
when the zonal flow is quasi-static and wave action is conserved.
