Hurricane Isabel (2003) made landfall along the North Carolina coastline on 18 September as a Category 2 Hurricane before moving north-northwestward and losing its tropical characteristics in western Pennsylvania. Isabel produced extensive damage and a number of fatalities as it moved inland and a substantial fraction of the damage and fatalities were due to high winds. On 18 September, the Hurricane Research Division (HRD) conducted the Wind Fields near landfall experiment as Isabel made landfall along the North Carolina coastline. During this experiment, the NOAA WP-3D aircraft collected high-resolution wind and radar data while land-based research teams from several universities (Texas Tech, Clemson, Oklahoma, and Florida) as well as the Center for Severe Weather Research deployed instrumented towers and portable radars along and just inland from the coastline. When combined with conventional National Weather Service observations, the aircraft, tower, and portable radar data provide an unusually good dataset for documenting the changes in kinematic structure of a landfalling storm. This paper will employ this unique landfall dataset to evaluate how well the Kaplan/DeMaria decay model (Kaplan and DeMaria 1995) simulated the changes in wind structure that occurred after Hurricane Isabel made landfall.