8C.1
A three-dimensional cloud-resolving numerical study of tropical cyclogenesis
Michael T. Montgomery, Colorado State University, Fort Collins, CO; and M. E. Nicholls and T. A. Cram
We consider the problem of how hurricanes come into being in the deep tropics. Although a key issue is to explain why most tropical disturbances fail to become hurricanes,we study as a first step the cyclogenesis process in a favorable thermodynamic environment with no vertical shear. This work forms a foundation for future studies examining the disruption of cyclogenesis by ambient vertical shear.
A three-dimensional cloud-resolving model is used to study the metamorphosis of a mid-level cyclonic vortex into a tropical cyclone. The initial vortex is assumed to originate from either the core of an easterly wave or a mesoscale convective vortex. The initial vortex is constructed to be in gradient and hydrostatic balance and the initial sounding is modeled after the Jordan mean hurricane sounding. In addition to presenting a diagnosis of the mean and eddy fields from the cloud resolving simulation, a balanced diagnosis of the vortex spin up is carried out using both the Eliassen balanced vortex model and the Asymmetric Balance (AB) model. Given the mean and eddy forcings from the cloud-resolving simulation the balance models account for both the downward development of the tangential wind field and the formation of the cyclone's warm core.
Sensitivity experiments with differing sea surface temperatures, initial vortex amplitudes, moisture distributions, thermodynamic profiles, etc. will be summarized.
Session 8C, Tropical Cyclogenesis (Parallel with Sessions 8A, 8B, and 8D)
Wednesday, 1 May 2002, 8:30 AM-10:30 AM
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