Can Existing Theory Explain How the Tropical Cyclone Wind Field Responds to Surface Roughening and Drying?

Abstract:

Tropical cyclones cause significant inland hazards, including wind damage and freshwater flooding, all of which depend strongly on the responses of the storm wind field at and after landfall. Forecasts of hazard risks on any timescale could be improved with a predictive theory for this wind field response. Existing theoretical predictions for the time-dependent response of storm intensity, as well as the equilibrium response of storm size and structure, have been tested over the open ocean but have yet to be applied to the response of a mature storm to landfall. Recent works have explained the transient responses of TC low-level wind field to surface roughening and drying in idealized axisymmetric ƒ-plane simulations. Here, these transient responses are used to evaluate their theoretical predictions. Emanuel (2012) intensification theory performs well in reproducing the intensity decay. The equilibrium storm size length scale V_p/ƒ, defining V_p using the actual maximum wind speed, can predict the transient response of storm size (radius of 34-kt) to surface roughening. For surface drying, storm size scales with the V_p/ƒ after ∼12h. Finally, existing structural theories can capture the evolution of the low-level wind field outside the convective inner region; the inner region is more complicated. Overall, results indicate the potentials for existing theory to predict how a tropical cyclone evolves after landfall.