A simple physically-based model to predict the radius of maximum wind from outer size

Abstract:

The radius of maximum wind (RMW) is arguably the most important measure of tropical cyclone size in terms of real world impacts. However, it is a notoriously difficult quantity to study, as it is noisy to observe directly in the turbulent inner-core and is poorly resolved in reanalyses and climate models. One potential avenue for improving our understanding and prediction of the RMW is to link it to a measure of the size of the outer circulation. The latter is more easily observed, better resolved in global models and reanalyses, and does not covary strongly with maximum wind speed. Recent advances have characterized the statistics of various measures of the size of the outer circulation and, further, developed a theoretical model for the radial structure of the tangential wind field. Using these new tools, here we present a novel physically-based method for predicting the radius of maximum wind from outer size. A hybrid physical-statistical approach is employed that marries the model’s underlying parametric dependence directly to observations to minimize bias. The model may be used as a viable first-order guess of the RMW in operations as well as for simulating realistic distributions of the RMW for risk assessment in a changing climate.