Dynamics of Tropical Cyclones

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This proposal aims to develop a deeper understanding of certain fundamental dynamical aspects of tropical cyclones, with special emphasis on the factors that determine their intensity and size. The approach will be based on the analysis of (mostly idealized) simulations using several numerical models, some relatively simple and others more sophisticated. The study will include an analysis of prominent storms with extreme sizes, such as Tropical Cyclone Tracy, an intense midget storm that devastated the Australian city of Darwin in 1974, and Hurricane Sandy, a less intense storm, but one with an enormous radius of strong winds that reeked havoc with a large area of the northeastern seaboard United States in 2012. At present, there is little understanding of the factors that determine the size of individual storms, but work already initiated during the earlier stage of the project points to a way forward in attacking this problem. A part of the study will investigate the possibility of a hypothetical steady-state storm; an approach that we believe may hold the key to answering several questions about tropical-cyclone size in general. An important question to be addressed is whether there is a mechanism for limiting the size of storms so that a steady state can be achieved in principle. The knowledge gained from the analyses can be expected to flow on to improved forecasts and it has also the potential to lead to an improved method for assessing the potential intensity of storms.