Baroclinic instability in a two-layer model with parameterized slantwise convection

Abstract

A two-layer primitive equation model with a parameterization for slantwise convection is used to study explosive cyclones. The major results are: 1) the two-layer model produces a realistic explosive cyclone, 2) the explosive deepening coincides with the formation of the "bent-back warm front,' 3) frontogenetic calculations reveal an indirect circulation due to "tilting' in the intense warm front, and 4) the quasi-Lagrangian heat and vorticity budgets indicate strong interaction of the lower- and upper-level flow during the rapid spinup stage. Convection leads to rapid frontogenesis and the formation of a bent-back warm front. The sudden surge of cold advection in the regions of the bent-back warm front then forces the upper-level heights over the cyclone center to fall in a rather dramatic way. Increased upper-level vorticity advection interacts with the low-level system, leading to explosive cyclogenesis. -from Authors