This project has three parts. First, a composite study will be conducted of the azimuthal helicity distribution in a group of tropical cyclones with respect to ambient vertical wind shear. A previous study of Hurricane Bonnie showed an enormous azimuthal asymmetry in helicity, with large helicity and intense supercell-like storms in the downshear direction. The goal is to examine the robustness of these results over a wide range of storms. Second, a detailed study will be carried out concerning the evolution of Hurricane Bonnie using an extensive set of airborne meteorological and radar data, and dropsonde observations, obtained during that storm. The goal is to understand how the storm maintained its intensity in the presence of strong ambient shear. Finally, the role of the helicity distribution on the formation and downshear re-formation of tropical storms will be examined. Radar observations will be obtained for a group of near-coastal tropical cyclones within range of continuous land-based radar. Tropical Storm Gabrielle (2001) will be one storm in the study. The goal is to examine the structure and evolution of individual thunderstorm cells within the cyclone in the presence of large helicity and how such cells influence the larger-scale cyclone circulation.
Broader impacts include the training of graduate students, support for graduate students to attend conferences and present their work, and dissemination of results in the refereed literature and at conferences. The research results will contribute to a greater understanding and better prediction of hurricanes. Project scientists and students will also give talks on hurricanes to lay groups as part of outreach efforts.
