Fundamental understanding of storm systems and, hence, improved predictions depend upon advances in knowledge of many interacting meteorological phenomena. In this study, the Principal Investigator proposes to investigate the effects of atmospheric thermal forcing in flow regimes that posses a "critical level". A critical level is the height at which the velocity of the ambient wind coincides with the propagation speed of atmospheric disturbances. Previous work has shown that critical levels can play an important role in triggering and/or maintaining convection. The Principal Investigator will use both theoretical investigations and numerical modelling to study the relationship between thermal forcing and atmospheric flows with critical levels and how these relate to the formation and maintenance of two diverse atmospheric storm systems -- mid-latitude squall lines and east coast wintertime cyclones. //