Evaluation of a Heuristic Model for Tropical Cyclone Resilience
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Authors
Reasor, Paul D.
Montgomery, Michael T.
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2015-05
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Abstract
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 continuous spectrum-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.
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The article of record as published may be found at http://dx.doi.org/10.1175/JAS-D-14-0318.1
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Meteorology (MR)
Meteorology
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The first author (P. D. R.) would like to acknowledge support from NSF ATM-0514199. Both authors would like to thank Dr. David Schecter for stimulating discussions that helped motivate this study and for his insightful comments on the manuscript, including the comment that motivated Eq. (15).We would also like to thank two anonymous reviewers for their substantive comments, which have helped clarify both thought and presentation. The second author (M. T. M.) would like to acknowledge support from NSF AGS-0733380, AGS-1313948, NOAA’s Hurricane Research Division, and the U.S. Naval Postgraduate School.
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Journal of the Atmospheric Sciences, Volume 72, pp. 1765-1782, May 2015.
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This 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.