Balanced Contributions to the Intensification of Hurricane Opal as Diagnosed from a GFDL Model Forecast

Abstract

Abstract Stationary and propagating asymmetric features of atmospheric or oceanic origin near a hurricane are known to have an impact on its evolution. Although theoretical and observational studies have investigated the influence of such features on hurricane intensification, the degree to which either environmental or near-core region asymmetries of heating, friction, or potential vorticity (PV), in contrast to symmetric processes, weaken or intensify a hurricane has not been established. The present study uses the symmetric balanced model formulation of Eliassen and its extension to asymmetric balance (AB) to evaluate the impact of heating and friction, as well as eddy fluxes, on the intensification of Hurricane Opal of 1995 in a Geophysical Fluid Dynamics Laboratory (GFDL) model forecast. The diagnostics are made in cylindrical coordinates, with the symmetric vortex as the basic state and asymmetries as the environment. The application of AB, which explicitly includes the effects of asymmetric heating...