The authors would like to thank Rick Taft, Paul Reasor, Scott Fulton, William Gray, John Knaff, Mark DeMaria, Frank Marks, Peter Dodge, Mel Nicholls, and Hung-Chi Kuo for many helpful comments and discussions. This work was supported by NSF Grant ATM-9729970 and by NOAA Grant NA67RJ0152 (Amendment 19).
Black, M. L., and H. E. Willoughby, 1992: The concentric eyewall cycle of Hurricane Gilbert. Mon. Wea. Rev.,120, 947–957.
Carnevale, G. F., and R. C. Kloosterziel, 1994: Emergence and evolution of triangular vortices. J. Fluid Mech.,259, 305–331.
Carr, L. E., III, and R. T. Williams, 1989: Barotropic vortex stability to perturbations from axisymmetry. J. Atmos. Sci.,46, 3177–3191.
Carton, X. J., and B. Legras, 1994: The life-cycle of tripoles in two-dimensional incompressible flows. J. Fluid Mech.,267, 53–82.
——, and J. C. McWilliams, 1989: Barotropic and baroclinic instabilities of axisymmetric vortices in a quasi-geostrophic model. Mesoscale/Synoptic Coherent Structures in Geophysical Turbulence, J. C. J. Nihoul and B. M. Jamart, Eds., Elsevier, 339–344.
——, G. R. Flierl, and L. M. Polvani, 1989: The generation of tripoles from unstable axisymmetric isolated vortex structures. Europhys. Lett.,9, 339–344.
Denoix, M.-A., J. Sommeria, and A. Thess, 1994: Two-dimensional turbulence: The prediction of coherent structures by statistical mechanics. Progress in Turbulence Research, H. Branover and Y. Unger, Eds., AIAA, 88–107.
Dodge, P., R. W. Burpee, and F. D. Marks Jr., 1999: The kinematic structure of a hurricane with sea level pressure less than 900 mb. Mon. Wea. Rev.,127, 987–1004.
Dritschel, D. G., 1989: On the stabilization of a two-dimensional vortex strip by adverse shear. J. Fluid Mech.,206, 193–221.
——, 1998: On the persistence of non-axisymmetric vortices in inviscid two-dimensional flows. J. Fluid Mech.,371, 141–155.
——, and D. W. Waugh, 1992: Quantification of the inelastic interaction of unequal vortices in two-dimensional vortex dynamics. Phys. Fluids A,4, 1737–1744.
Flierl, G. R., 1988: On the instability of geostrophic vortices. J. Fluid Mech.,197, 349–388.
Gent, P. R., and J. C. McWilliams, 1986: The instability of barotropic circular vortices. Geophys. Astrophys. Fluid Dyn.,35, 209–233.
Kloosterziel, R. C., and G. J. F. van Heijst, 1991: An experimental study of unstable barotropic vortices in a rotating fluid. J. Fluid Mech.,223, 1–24.
Koumoutsakos, P., 1997: Inviscid axisymmetrization of an elliptical vortex. J. Comput. Phys.,138, 821–857.
Kuo, H.-C., R. T. Williams, and J.-H. Chen, 1999: A possible mechanism for the eye rotation of Typhoon Herb. J. Atmos. Sci.,56, 1659–1673.
Lamb, H., 1932: Hydrodynamics. 6th ed. Cambridge University Press, 738 pp.
Larichev, V. D., and G. M. Reznik, 1983: On collisions between two-dimensional solitary Rossby waves. Oceanology,23, 545–552.
Legras, B., P. Santangelo, and R. Benzi, 1988: High resolution numerical experiments for forced two-dimensional turbulence. Europhys. Lett.,5, 37–42.
Melander, M. V., J. C. McWilliams, and N. J. Zabusky, 1987a: Axisymmetrization and vorticity-gradient intensification of an isolated two-dimensional vortex through filamentation. J. Fluid Mech.,178, 137–159.
——, N. J. Zabusky, and J. C. McWilliams, 1987b: Asymmetric vortex merger in two dimensions: Which vortex is “victorious”? Phys. Fluids,30, 2610–2612.
Montgomery, M. T., and L. J. Shapiro, 1995: Generalized Charney–Stern and Fjørtoft theorems for rapidly rotating vortices. J. Atmos. Sci.,52, 1829–1833.
——, and R. J. Kallenbach, 1997: A theory for vortex Rossby-waves and its application to spiral bands and intensity changes in hurricanes. Quart. J. Roy. Meteor. Soc.,123, 435–465.
——, and J. Enagonio, 1998: Tropical cyclogenesis via convectively forced vortex Rossby waves in a three-dimensional quasigeostrophic model. J. Atmos. Sci.,55, 3176–3207.
Orlandi, P., and G. J. F. van Heijst, 1992: Numerical simulations of tripolar vortices in 2d flow. Fluid Dyn. Res.,9, 179–206.
Polvani, L. M., and X. J. Carton, 1990: The tripole: A new coherent vortex structure of incompressible two-dimensional flows. Geophys. Astrophys. Fluid Dyn.,51, 87–102.
Reasor, P. D., M. T. Montgomery, F. D. Marks, and J. F. Gamache, 2000: Low-wavenumber structure and evolution of the hurricane inner core observed by airborne dual-Doppler radar. Mon. Wea. Rev.,128, 1653–1680.
Rossi, L. F., J. F. Lingevitch, and A. J. Bernoff, 1997: Quasi-steady monopole and tripole attractors for relaxing vortices. Phys. Fluids,9, 2329–2338.
Samsury, C. E., and E. J. Zipser, 1995: Secondary wind maxima in hurricanes: Airflow and relationship to rainbands. Mon. Wea. Rev.,123, 3502–3517.
Schubert, W. H., M. T. Montgomery, R. K. Taft, T. A. Guinn, S. R. Fulton, J. P. Kossin, and J. P. Edwards, 1999: Polygonal eyewalls, asymmetric eye contraction, and potential vorticity mixing in hurricanes. J. Atmos. Sci.,56, 1197–1223.
Shapiro, L. J., and H. E. Willoughby, 1982: The response of balanced hurricanes to local sources of heat and momentum. J. Atmos. Sci.,39, 378–394.
Smith, G. B., and M. T. Montgomery, 1995: Vortex axisymmetrization: Dependence on azimuthal wavenumber or asymmetric radial structure changes. Quart. J. Roy. Meteor. Soc.,121, 1615–1650.
Sutyrin, G. G., 1989: Azimuthal waves and symmetrization of an intense vortex. Sov. Phys. Dokl.,34, 104–106.
van Heijst, G. J. F., R. C. Kloosterziel, and C. W. M. Williams, 1991:Laboratory experiments on the tripolar vortex in a rotating fluid. J. Fluid Mech.,225, 301–331.
Willoughby, H. E., 1990: Temporal changes of the primary circulation in tropical cyclones. J. Atmos. Sci.,47, 242–264.
——, J. A. Clos, and M. G. Shoreibah, 1982: Concentric eyewalls, secondary wind maxima, and the evolution of the hurricane vortex. J. Atmos. Sci.,39, 395–411.
——, J. M. Masters, and C. W. Landsea, 1989: A record minimum sea level pressure observed in Hurricane Gilbert. Mon. Wea. Rev.,117, 2824–2828.