27th Conference on Hurricanes and Tropical Meteorology

14B.7

Axisymmetric tropical cyclogenesis via a single convective ring

Thomas Frisius, Johann Wolfgang Goethe-Universitšt Frankfurt am Main, Frankfurt am Main, Germany

High resolution simulations of tropical cyclones within an axisymmetric nonhydrostatic model reveal that a single convective ring can generate a tropical cyclone. This appears when the initial temperature profile is neutral to convective instability. As a consequence, the first convection cell occurs near the radius of maximum wind. Afterwards the convective ring contracts and converts into the tropical cyclones' eyewall. It appears that the potential radius of the ring remains almost fixed during the intensification process. Therefore, the angular momentum of the ring is approximately conserved. The mechanism of this process can be understood in terms of a simple axisymmetric balanced model based on the zero potential vorticity assumption. The strong wind intensification rate results from the large heating gradient at the outer side of the convective updraft. Radial momentum diffusion is necessary to prevent a frontal collapse inside of the ring. This kind of cyclogenesis is inconsistent with the CISK and WISHE theory for tropical cyclogenesis since in both theories an interaction between the vortex and many convection cells is proposed.

extended abstract  Extended Abstract (812K)

Session 14B, Tropical Cyclogenesis IV
Thursday, 27 April 2006, 3:30 PM-5:30 PM, Regency Grand Ballroom

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