Title: The Role of the Mid-Level Vortex in Tropical Cyclogenesis

Abstract: Tropical cyclogenesis may be defined as the development and intensification of a low- level, warm-core vortex over (relatively) warm ocean water. Baroclinic processes may be involved in the formation of higher latitude cyclones and polar lows, but these processes are not necessary and generally do not occur in the low latitude regions associated with the formation of tropical cyclones. Based on observations of cyclogenesis in the tropical east Pacific, Bister and Emanuel postulated a mechanism for cyclogenesis in which the low-level vortex forms in a region moistened and stabilized by stratiform rain. Rain of this type typically occurs in the decaying phase of a large mesoscale convective system. Such systems generally spin up a mid-level vortex due to mid-level inflow.
A great deal of observational and modeling data suggest that cyclogenesis is associated with the prior formation of a mid-level vortex. Two recent field programs, TPARC/TCS08 in the west Pacific and PREDICT in the Atlantic and Caribbean, have provided observations of unprecedented quality, allowing us to unravel many of the aspects of tropical storm formation. The picture painted by Bister and Emanuel of tropical cyclogenesis appears to be correct as far as it goes. I will present the results of complete vorticity and thermodynamic analyses as well as numerical simulations of convection in tropical cyclogenetic conditions that reveal new aspects of this process.

Host: Marty Singh
Speaker's website: http://www.physics.nmt.edu/~raymond/