Petterssen's "Type B' cyclogenesis in terms of discrete, neutral Eady modes

We investigate B. Farrel's hypothesis that the development of a surface cyclone with the passage of an upper trough, as observed by S. Petterssen and coworkers, may be understood in terms of an initial-value problem on the Eady model. We consider the response of the Eady model to perturbations whose horizontal wavelengths are short enough to ensure their stability, and whose perturbation potential vorticity is zero. The amplification of the surface trough is not due to mere geometrical interference, but rather is the consequence of an energy-exchanging interplay between waves and mean flow. This distinction is emphasized by comparison with a model in which a superficially similar phenomenon occurs, but without such an interplay. -from Author