Tropical Cyclone Marine Surface Wind Modeling: The Shape of the Radial Wind Profile Matters

Methods of analysis and modeling of the distribution of surface winds about tropical cyclones have increasingly recognized the deficiency of the classical representation of the radial distribution of (e.g. "Rankine vortex", "Holland profile") of a linear increase of wind speed from the center to a single and tight radius of maximum and a sharp decay to the ambient flow. Newer analysis schemes and parametric and dynamical models now attempt to allow for more complex radial distributions including the possibility of multiple radial wind maxima and storms with indistinct radial maxima and shelf-like profiles extending far into the ambient flow. This paper demonstrates the rather high degree of skill with which a representation of the radial pressure profile with a double exponential form within the initialization scheme of the widely applied "TC96" steady state planetary boundary model (PBL) succeeds in modeling such wind field complexities as well as the large range of wind field spatial scales associated with have come to be known as "compact", "incompact" and "annular" cyclones, and in representing the life cycle of storms that undergo rapid dynamic transformation in wind structure associated with the eye-wall replacement cycle and transitory storm encounters with land masses. Examples are drawn from recent well monitored U.S. Gulf and East Coast historical hurricanes, but the characteristics demonstrated appear to apply to tropical cyclone worldwide.