Cyclogenesis in polar air streams.

Abstract

2 case studies of cyclogenesis that occurred in polar air streams behind or poleward of major frontal bands are presented. Based on the results of the studies, and on other evidence, characteristics of the type of disturbance in question are described. Instability mechanisms for their formation are discussed. It is concluded that they are primarily a baroclinic phenomenon that owe their below average size to the effect that small static stabilities at low levels have in reducing the wavelenght of maximum instability and to the fact that they develop on already perturbed large-scale states rather than on uniform zonal flows. Conditional instability of the second kind and barotropic instability cannot be ruled out as possible important additional influences in their formation. -from Author