Considerable attention has been given to the transition of tropical cyclones to extratropical cyclones in the recent literature. These storms typically contain heavy rainfall and strong winds. Such transitions are often not well forecast by operational models. Further complications arise as the tropical cyclone transitions 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 from eastern VA to eastern PA. This rainband developed well in advance of Agnes. This band occurred along a north-south oriented baroclinic zone that developed in place east of the Appalachian Mountains. The Pennsylvania State University/National Center for Atmospheric Research Mesoscale Model (MM5) is used examine the transition of Hurricane Agnes as well as the generation of the baroclinic zone ahead of Agnes. The object is to examine the mesoscale structure associated with the development of the heavy rain band extending northward from Agnes. High resolution simulations will be used to examine to the importance of diabatic heating in the formation of the baroclinic zone. The sensitivity of the simulation to the choice of cumulus parameterizations will also be examined.