Collaborative Research: Extratropical Transition of Atlantic Tropical Cyclones: An Examination of the Factors Influencing Transition and Post-Transition Intensity Change

This research is being done in collaboration with Dr. Christopher Velden of the University of Wisconsin. Extratropical transition of tropical cyclones is a poorly understood process, yet the resulting systems can have a tremendous impact on the weather in the northeastern U.S. and Canada, producing intense flooding rains, wind storms and wave damage. As a tropical storm transitions into an extratropical storm, its structure changes from a nearly axisymmetric cyclone with maximum winds near the surface to a highly asymmetric cyclone with strongest winds aloft. The transitions often involve interactions with surface fronts or upper level troughs or may result from mergers with pre-existing extratropical storms. The principal investigators will investigate the transition process by examining a number of observed cases of transitions to document the life cycle and structural changes and by conducting model simulations with a state-of-the-art mesoscale model. As part of this effort, they will test a variety of conceptual models of the transition process. A major new resource they will exploit is the availability of AMSU satellite data. These data will be used to derive thermal profiles and wind fields that will be incorporated into the model simulations. It is hoped that a better understanding of the transition process will improve forecasts.