The dynamics of intensification in an HWRF simulation of Hurricane Earl (2010)

We use a high resolution numerical simulation of Atlantic Hurricane Earl (2010) to assess the applicability of a recent paradigm for tropical cyclone intensification to understand Earl's intensification in relatively strong vertical shear. The integrity of the simulation is judged by comparing analyses thereof with those of the unprecedented observational data gathered in Earl. Consistent with the conventional view of spin up, the amplification of the tangential wind field above the boundary layer occurs as the absolute angular momentum surfaces are drawn inwards by the aggregate heating of the rotating convective clouds in the interior of the vortex. In addition to this conventional pathway, spin up occurs within the inner-core boundary layer and the maximum tangential winds are found there. The latter is another element of the new paradigm. The presence of vertical shear during Earl's rapid intensification introduces eddy processes in addition to the intrinsic eddy processes found previously in a quiescent environment associated with vortical plume and related wave and filamentary vorticity structures in and around the developing eyewall region. Despite the detrimental influence of the shear on the vortex alignment, the combined eddy processes are shown to contribute to a contracting storm and an enhanced overturning circulation.