Reexamination of Eyewall Instabilities in Simulated Hurricanes

Because eyewall asymmetries and mesovortices can be associated with fluctuations in maximum wind speed, it is important to understand the factors that control their development and evolution. However, most fundamental studies have not fully incorporated the effects of surface fluxes and the moist secondary circulation. In this study, we expand on previous works by using a three-dimensional cloud model to examine the stability of mature, steady-state hurricanes produced by axisymmetric simulations. The primary goal is to understand how the moist secondary circulation—coupled to surface processes—may affect the development of asymmetry and the attendant change in hurricane intensity. To help achieve this goal, results from our numerical simulations are compared to complementary simulations in which moisture and surface processes are removed. In addition, we examine the sensitivity of eyewall asymmetries to variations in the turbulence parameterization and the surface exchange coefficients of enthalpy (c_e) and momentum (c_d). This work is supported by NSF grand AGS-1101713.