Diagnostic Studies of Spiral Rainbands in a Nonlinear Hurricane Model

Abstract

Results from diagnostic studies of a nonlinear hurricane model support the conclusion that internal gravity-inertia waves are responsible for hurricane rainbands. The mean relative vorticity differed little between the bands and their environment, a characteristic of gravity waves modified slightly by the earth's rotation. Small differences in mean radial and tangential velocity components, divergence, and the radial pressure gradient force were noted between the bands and their environment. The upper layers of the bands were responsible for a small increase in the model storm's kinetic energy due to a net convergence of kinetic energy flux from the environment into the bands. A large net convergence of cyclonic angular momentum flux into the bands occurred in the boundary layer. Conversion of available potential energy to kinetic energy was not significant in the model bands. Finally, latent heating in the bands did not play an important role in the maintenance or propagation of the bands at large radii.