On the Asymmetries of Hurricane Cores

Current understanding of hurricane intensity is largely based on axisymmetric MPI theory. Nevertheless, asymmetric features can appreciably affect the strength of the primary circulation. Core instability is one proposed cause of asymmetric perturbations. While some progress has been made toward understanding the mechanisms of asymmetric core instability (ACI), much more can be learned. This presentation will selectively review existing theories of ACI. It will be seen that most rely on debatable simplifications that either neglect or crudely incorporate the following factors: (i) overturning circulation, (ii) coupling of "free-tropospheric" and boundary layer disturbances, and (iii) diabatic "forcing" associated with the perturbation of internal cumulus convection. Preliminary numerical experiments designed to test the adequacy of these simplifications will be discussed. Sensitivity of ACI to model parameters will also be addressed. This work is supported by NSF grants AGS-0750660 and AGS-1101713.