The Critical Role of Air-Sea Enthalpy and Momentum fluxes in Tropical Cyclone Intensity and Structure

I review theoretical, modeling and observational evidence that tropical cyclone intensity, and to some extent structure, are strongly modulated by air-sea fluxes of both enthalpy and momentum. In particular, theory and models for which ambient conditional instability plays little or no role are especially sensitive to surface fluxes, with intensity being largely controlled by fluxes under the eyewall. On the other hand, models for which ambient conditional instability plays a larger role are less sensitive to fluxes under the eyewall. The observed maintenance of hurricane intensity in some storms that are largely over land but whose eyewalls remain over the ocean support the former view. The critical need to parameterize surface fluxes in very high wind speed conditions, and CBLASTs attempt to make the measurements needed to formulate such parameterizations will also be discussed.