During the California Landfalling Jets Experiment (CALJET), the NOAA P-3 aircraft was used to obtain measurements of surface momentum and heat fluxes, and to document the boundary layer structure associated with maritime cyclones. Operational, climatological and special sites are used to document the coastal precipitation associated with the landfalling phase of the storms. On February 6-7, 1998, the aircraft obtained a detailed north-south cross-section of the atmospheric structure and boundary-layer fluxes in the cold-air region between two large maritime cyclones. These observations are used to validate several planetary boundary layer (PBL) schemes used in numerical simulations of this case with the Penn State/NCAR Mesoscale Model (MM5). These PBL schemes include the Burk-Thompson scheme, the Blackadar scheme, and the operational Medium-Range Forecast (MRF) model scheme. The results show significant differences in the offshore PBL depth and surface heat fluxes between the schemes. In addition, the coastal precipitation can vary by as much as 50% from one scheme to another in some locations. Additional numerical experimentation is done to understand the relationship between the coastal precipitation and the oceanic heat fluxes.