An Unsung Mechanism for Frontogenesis and Cyclogenesis

Abstract

It is suggested that the constructive interference of a wave packet of stable normal modes could constitute a mechanism for local fronto- and cyclogenetic development. The potential efficacy of this mechanism is illustrated by deriving an analytical solution for the nonlinear two-dimensional, semigeostrophic evolution of such a packet within a uniformly sheared flow. The solution is itself of intrinsic interest and embodies the rapid formation of both a strong surface frontal structure and a shallow cyclonic warm-core system. Cursory consideration of the balanced flow evolution of a localized three-dimensional perturbation implanted within a baroclinic zone also provides evidence for the postulated mechanism.