The Dynamics of Complexly Sheared Tropical Cyclone Convection and Relationships with Tropical Cyclone Evolution

The localized kinematic and thermodynamic conditions in a tropical cyclone (TC) can vary considerably in space and time. This variability supports a spectrum of convective cloud and rainband morphologies and dynamics within a TC. For example, the typical azimuthal-mean kinematic structure of a TC vortex means that both the horizontal and vertical shear of the horizontal wind typically varies substantially from the inner-core to the outer rainband region. Understanding how the behavior of convection and rainbands varies in a TC is especially important since the distribution of latent heating, convection-induced circulations, and their cold pools can impact the structure and intensity of a TC. To contribute to a better understanding of these complexities, a convection-resolving WRF simulation of a TC and the idealized Bryan Cloud Model (CM1) are used to study basic aspects of convective morphology in complex kinematic and thermodynamic environments.

The idealized WRF simulation contains various features of a typical intense TC, such as rapid intensification and structure change. Here, the kinematic and thermodynamic conditions variations throughout the TC are documented. The characteristics and life cycles of convective elements and rainbands are studied with respect to their surrounding horizontal and vertical wind shear values. The impacts of instability and relative humidity on convection are analyzed as well.

To shed light on the results in the WRF simulation, the CM1 is employed to isolate the impacts of various TC-induced factors on individual convective cells. In particular, the behavior of convection in the midst of various horizontal and vertical wind shear profiles is reexamined, with a focus on the sensitivity of complexly sheared convection to thermodynamic variations. These idealized simulations add insight into convective processes in the rapid filamentation zone, outer rainband regions, and potentially eyewall regions as well.