Extended Abstract (2.0M)7A.2
An examination of the mesoscale structure associated with the extratropical transition of Hurricane Agnes (1972)
Michael J. Dickinson, SUNY, Albany, NY; and L. F. Bosart
Considerable attention has been given to the transition of tropical cyclones to extratropical cyclones in the recent literature. Transition often occurs when the tropical system passes over cooler water (or land) and interacts with a mid-latitude trough. Such transitions are often not well forecast by operational models. Over land, the low-level circulation associated with the transitioning storm can interact with terrain or a surface baroclinic zone, resulting in localized regions of intense precipitation. These regions can often extend several hundred kilometers away from the storm center, providing another challenge to forecasters. One of the interesting aspects regarding the transition of Hurricane Agnes (1972) over the southeastern United States was the exceptionally heavy rainfall that developed east of the Appalachian mountains from eastern VA to eastern PA. This heavy rainfall developed well in advance of the Agnes circulation. The intent of this study is the examine both the synoptic and mesoscale features, as well as the distribution of precipitation associated with the extratropical transition of Agnes, using the Pennsylvania State University/National Center for Atmospheric Research Mesoscale Model (MM5). High-resolution simulations will be used to ascertain the roles of the Agnes circulation, upper-level trough, and local terrain in the development of the intense precipitation during this event.
Session 7A, Tropical Cyclones
Wednesday, 14 August 2002, 10:30 AM-11:45 AM
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