Interaction Between Two Concentric Potential Vorticity Rings – Implications to the Evolution of Hurricane Concentric Eyewall

Once the concentric eyewall developed in a hurricane, the primary and secondary eyewalls would interact each other. Such an interaction has been studied previously with the assumption of a monopolar potential vorticity (PV) core of the primary eyewall using a nondivergent barotropic model. However, recent high resolution numerical model simulations show that the primary eyewall often displays an annular PV ring structure, satisfying the necessary condition for barotropic instability. In this case, the interaction between the two PV rings, respectively, corresponding to the inner and outer eyewall in a hurricane, could be very different. In this study, the interaction between two PV rings is investigated using a shallow water equation model. It is found that the interaction between the two PV rings could be quite different from the previously studied interaction between the stable PV core and a secondary PV ring. Because of the instability nature of both PV rings in our study, the existence of one PV ring generally destabilizes the other ring, resulting in quite different flow regimes and shortening the lifecycle of the concentric PV structure. Implications of the findings will be discussed at the conference.