Assessment of tropical cyclone structure variability

The landfall of large hurricanes in densely populated areas has increased the awareness that tropical cyclone struc-ture plays an important role in the destructive potential of a storm. A unique set of H*Wind analyses of Atlantic tropical cyclones during the 2003-2005 seasons is studied to better understand the internal and external mechanisms that lead to significant variability in surface wind structure. Secondary eyewall formation, asymmetric convection, land interaction, and environmental vertical wind shear were generally found to be mechanisms for radius of maximum wind increases, intensity decreases, and size of the radius of 34-kt wind increases. Two modes of size changes were documented that may lead to 100 km increases in 12-24 h, or near-zero size changes when a sharper than average outer wind structure profi les are generated. The statistical relationships among the radius of maximum wind, intensity, and outer-core wind structure from this sample may provide perturbed vortex initial conditions for an ensemble model to predict structure changes.