Thursday, 13 February 2003
Lessons from landfalling and transitioning tropical cyclones
Landfalling and transitioning tropical cyclones pose a major forecast challenge in terms of storm track and intensity, the timing and location of the extratropical transition, and the expected regions of coastal and inland flooding associated with storm-related heavy precipitation. Flooding is an especially significant forecast challenge when a tropical cyclone makes landfall and then undergoes an extratropical transition while still over land or in the immediate coastal waters. In these situations (e.g., Hurricane Floyd of 1999) the inland flooding, especially if the ground is already saturated from previous heavy rains, can be more severe and lead to a greater loss of life and damage than the immediate coastal damage associated with high winds, the storm surge, and heavy rain.
The focus of this paper will be on analyses of characteristics of heavy precipitation associated with landfalling and transitioning tropical cyclones and the dynamics of the extratropical transition process. In particular, we will show that the distribution of precipitation relative to the storm track after landfall is strongly influenced by the dynamical structure of the evolving synoptic scale flow and that the dynamics of the transition process are quite sensitive to the presence of upstream upper-level potential vorticity anomalies and downstream jet-entrance regions. Examples will be drawn from recent storms including Danny (1997), Dennis (1999), Floyd (1999), Irene (1999) and Michael (2000).