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Exploring the dynamics of how coastal downwelling can lead to landfalling hurricane intensification
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  • Lewis Gramer,
  • Jun Zhang,
  • Ghassan Alaka,
  • Andrew Hazelton,
  • Hyun-Sook Kim,
  • Sundararaman Gopalakrishnan
Lewis Gramer
Cooperative Institute for Marine and Atmospheric Studies Miami

Corresponding Author:[email protected]

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Jun Zhang
University of Miami
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Ghassan Alaka
NOAA/AOML/Hurricane Research Division
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Andrew Hazelton
Atlantic Oceanographic and Meteorological Laboratory
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Hyun-Sook Kim
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Sundararaman Gopalakrishnan
Atlantic Oceanographic and Meteorological Laboratory
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Our prior analysis of a coupled tropical cyclone (TC) air-sea model (HWRF-B) revealed three cases in the 2020 Atlantic hurricane season where coastal downwelling - developing ahead of a TC - contributed to the intensification of each TC as it approached landfall. Coastal downwelling is a specific oceanographic mechanism: we briefly consider other mechanisms potentially contributing to this “shelf effect”, including coastal trapped waves and near-surface advection. We then present preliminary results from a further analysis of HWRF-B forecasts from the 2017-2020 Atlantic and east Pacific hurricane seasons, evaluating the prevalence of the shelf effect for TCs interacting with continental and insular coasts in these two ocean basins. We explore mechanisms linking shelf SST sustenance with inner core convective development and storm intensification, using both a detailed energy budget and Lagrangian tracking experiments within the boundary layers of case study storms. Finally, we briefly discuss the implications these findings hold for evaluating new coupled TC forecast modeling systems currently being developed as a part of the Hurricane Forecast Improvement Program (HFIP).