The intensification of cyclones from asymmetric heating revisited: energetics and weakly nonlinear effects

The intensification of tropical cyclones is driven almost entirely from the latent heat released in cumulus convection around the core of the storm. While the wind and pressure fields can be quite symmetric around the storm center, the convection and its associated heating is almost always highly asymmetric. Nonetheless, this highly asymmetric heating leads to intensification of the symmetric vortex.

In previous work, the first author and collaborators used a linearized model of nonhydrostatic dynamics to study the effects of symmetric and asymmetric heating on balanced vortices. In contrast to previous studies using vorticity perturbations in two-dimensional or quasi-balanced models, the effects of the asymmetric part of the forcing were found to be very small, and almost always negative in regards to intensity change.

This issue is revisited as we more closely examine the changes in the kinetic and available potential energies of the balanced vortex when forced by asymmetric heating. In some cases, purely asymmetric heating does lead to a net increase in KE of the symmetric vortex, even though the maximum wind speed at the surface decreases. Though still quite small in amplitude, these changes in the wind field can also enhance the development from subsequent heating events.