83rd Annual

Thursday, 13 February 2003
On the significance of hot towers, vortex tube stretching, low-level vortex mergers, and vortex Rossby waves in tropical cyclogenesis
Michael T. Montgomery, Colorado State University, Fort Collins, Colorado; and M. N. Nicholls, T. Cram, A. Saunders, and P. D. Reasor
In this talk we summarize current research examining the problem of tropical cyclogenesis in both idealized and realistic environments. With only modest background cyclonic vorticity supplied either by an elevated mesoscale convective vortex or a low-level tropical disturbance we find that convective "hot towers" and the vertically extensive mesovortices generated by them constitute the primary building blocks of a tropical cyclone. We believe the tropical cyclogenesis problem is thus essentially one of assembling and axisymmetrizing the vorticity anomalies generated by the deep convective hot towers.

The idea of mesoscale organization via the generation of vortical hot towers and their merger/axisymmetrization is motivated by recent satellite and airborne Doppler radar observations and diagnostic analyses of high-resolution cloud-resolving numerical simulation experiments using both MM5 and RAMS. The idea is supported through the application of balanced diagnoses and local tangential momentum budgets centered on key organizational "events" during the high-resolution numerical simulations.

Although we focus primarily here on the intrinsic mesoscale organizational processes in relatively ideal (favorable) environments, we believe insight derived from this research will prove useful in understanding how these organizational processes are hampered in more hostile "storm killer" environments, such as high vertical shear of the ambient flow.

Future theoretical and observational tests of the vortical hot tower theory are proposed.

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