Aspects of chaotic mixing in the hurricane inner-core

Potential vorticity (PV) mixing episodes resulting from the dynamic breakdown of the hurricane PV hollow tower serve as efficient mechanisms of redistributing PV from the eyewall, where it is created by diabatic heating, into the eye. These episodes can have significant effects on the intensity of the storm since by inversion PV may be partitioned into both inertial and static stability. This breakdown can also create persisent eye mesovortices which can serve as transporters of moist entropy from the eye into the eyewall. In addition to other internal processes such as concentric eyewall cycles, accurate forecasting of intensity fluctuations of strong hurricanes is currently limited by an incomplete dynamical understanding of this chaotic advective process.

A hierarchical modeling approach is undertaken to understand some basic dynamics of this problem. First, an effective diffusivity diagnostic tool is applied to unforced barotropic vorticity ring breakdowns in order to identify and characterize basic flow regimes during PV mixing events. While this tool shows many chaotic mixing regions, in particular we seek to determine the existence and magnitude of partial barrier regions where flow trajectories are integrable. Understanding the transient location and magnitudes of both these regions clarifies how a passive tracer, such as water vapor, is asymmetrically mixed between the eye and eyewall during PV hollow tower breakdowns. Secondly, this mixing process is examined in a dry quasi-static primitive equation model using unforced hurricane-like PV hollow towers. The preferred isentropic layers for mixing are examined and wave-mean flow diagnostics are presented to understand how these events change the mean vortex intensity.