Detailed observations of boundary layer structure and processes were acquired on 13-14 September 2001, during the landfall of Tropical Storm Gabrielle. The UAH Mobile Integrated Profiling System (MIPS) and the Shared Mobile Atmospheric Research and Teaching Radar (SMART-R) were co-located along the west Florida coast line at Venice at a site very close to the circulation center at landfall. These measurements are analyzed to compare the highly-variable boundary layer properties in various locations of the rapidly evolving tropical storm. The off-shore, easterly flow was rendered stable by previous rainfall evaporation and mesoscale downdrafts within an extensive stratiform precipitation shield that preceded the arrival of the Gabrielle’s core. In contrast, the on-shore flow on the western side of the circulation produced an unstable, turbulent boundary layer that exhibited a well-defined top varying between 500-700 m MSL. The horizontal variability of the each boundary layer is examined using MIPS observations and high-resolution Doppler radar scans at locations up to 15 km on either side of the coastline. These analyses reveal the transitions in boundary layer structure from land to water, and water to land, for each of the regimes. Analyses of two additional boundary layer phenomena include gravity waves that were associated with strong flow in the stable boundary layer of the off-shore flow, and boundaries, that resembled warm and cold fronts, associated with the landfall of Gabrielle. The warm frontal boundary was directly associated with tornadoes that formed along the west coast during landfall.