Evaluation of a Heuristic Model for Tropical Cyclone Resilience
Reasor, Paul D.
Montgomery, Michael T.
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This work examines the applicability of a previously postulated heuristic model for the temporal evolution of the small-amplitude tilt of a tropical cyclone–like vortex under vertical shear forcing for both a dry and cloudy atmosphere. The heuristic model hinges on the existence of a quasi-discrete vortex Rossby wave and its ability to represent the coherent precession and tilt decay of a stable vortex in the free-alignment problem. Linearized numerical solutions for a dry and cloudy vortex confirm the model predictions that an increase in the magnitude of the radial potential vorticity (PV) gradient within the vortex skirt surrounding the core yields a more rapid evolution of a sheared vortex toward the equilibrium, left-of-shear tilt configuration. However, in the moist-neutral limit, in which the effective static stability vanishes in rising and sinking regions, the heuristic model yields a poor approximation to the simulated vortex core evolution, but a leftof- shear tilt of the near-core vortex, radially beyond the heating region, remains the preferred long-time solution. Within the near-core skirt, the PV perturbation generated by vertical shearing exhibits continuousspectrum- type vortex Rossby waves, features that are not captured by the heuristic model. Nevertheless, the heuristic model continues to predict the rapid vertical alignment and equilibrium, left-of-shear tilt configuration of the simulated near-core vortex in the moist-neutral limit.
The article of record as published may be found at http://dx.doi.org/10.1175/JAS-D-14-0318.1
RightsThis publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.
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