Climatology and Analysis of the Decay of Tropical Cyclones Making Landfall in the U.S. from the Atlantic Basin

While coastal areas along the United States Atlantic and Gulf Coasts have become increasingly accustomed to dealing with landfalling hurricanes and tropical storms, populations further inland can often be surprised by powerful storms that retain their intensity more than forecast. Hurricane Ike in 2008 is one of the more recent examples of such surprise, as it generated gusts to hurricane force well into the Ohio Valley after interaction with an unusually strong baroclinic trough. Considerable research has studied the development and intensification of hurricanes; however, there is a comparative lack of research on the topic of the variety in their decay over land. Statistical studies of the decay problem date back to the 1950s, and many of the tropical cyclone modeling studies of the 1960s and 1970s refined the debate as to the primary cause of overland decay (or intensification) of tropical cyclones. Several seminal works have created a partial climatology of the overland decay of cyclones in the Atlantic basin; however, few have been comprehensive in nature and none have examined in detail the characteristics associated with anomalous decay rates. This study presents that comprehensive climatology based on all available reliable tropical cyclone data in the Best Track Data Set. The mean decay rate of US landfalling tropical cyclones between 1950 and 2006 (in terms of pressure and wind decay), its variability in time and space, and its overall distribution, are determined empirically once the storm makes landfall along the coastline. The second focus of this study is to analyze the particular characteristics of a storm and the synoptic setup that allow the TC to maintain strength (or weaken unusually quickly) while traversing a landmass. The size, structure, and strength at landfall of storms that exhibit an abnormally slow or fast decay rate will be analyzed and physically interpreted to determine what enables a TC to retain or lose an unusual fraction of its strength. Composite maps of the synoptic setup associated with slowly and quickly decaying storms, normalized to the point of landfall, will lend insight into how the environment contributes to their anomalous decay.