Fig. 15d. Maxumum perturbation kinetic energy for any complex phase velocity at each streamwise wavelngth (top); and corresponding phase velocities and growth rates (bottom) in a bartopically unstable westerly jet. Maximum growthrate falls at a wavelength of about 3 times the jet's half width. The fastest growing wave proagates downstream with ~ 0.41 of the strongest wind at the jet axis and grows at a rate of 0.41 of the inverse timescale defined by the maximum wind divided by the jet's half width.