Easterly Wave-Itcz Interaction and Tropical Cyclone Formation over the Atlantic

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A large number of Atlantic tropical cyclones, especially the most dangerous hurricanes, develop from easterly waves over the Atlantic Main Development Region (MDR: 10-20N, 20-80W), along the northern edge of the Intertropical Convergence Zone (ITCZ). The close proximity between the ITCZ axis and the wave track allows ITCZ-wave interaction on different time scales. This project aims to study the interaction between the ITCZ and easterly waves over the Atlantic and the impacts of their interaction on subsequent storm development. In particular, easterly waves will be examined as a "connecting link" between the large-scale circulation and tropical cyclone formation. The statistical aspects of the link are relatively well-known, but the dynamical and thermodynamical mechanisms are not. This project consists of observational analysis and numerical modeling that focus on a set of testable hypotheses on ITCZ-wave interaction and tropical cyclone formation. The investigators will use insights from their recently developed marsupial framework to examine how the variability of the Atlantic ITCZ affects tropical cyclogenesis in the Atlantic MDR by altering the existence and morphology of the wave "pouch". The emphases are on the structure and evolution of the wave pouch, and ITCZ-wave interaction in a multi-scale framework. The wave pouch is a region of approximately closed Lagrangian circulation within the wave's critical layer and is shown by our previous studies to be a necessary condition for storm formation. Broader impacts of this work are in advancing our understanding of the impacts of the large-scale circulation on tropical cyclone formation and variability, which can ultimately contribute to improved tropical cyclone forecasts and to studying tropical cyclone activity in a changing climate. The proposal will train and support one graduate student.