As part of the CLIMODE observational program, a fixed surface mooring was deployed in the Gulf Stream (38N, 65W) for 15 months. Air-sea measurements (1 minute sampling), including radiation, and subsurface oceanographic data (5 minutes sampling) were collected. These high quality and long term measurements are the first of their kind in this region where high winds and strong currents are common. Air-sea fluxes were computed using the COARE bulk parameterization. Wintertime oceanic heat loss events in excess of 1500 W/m2 occurred during cold air outbreaks when SST was high. We describe here the time variability of the marine boundary layer surface conditions and their evolution with respect to the relative position of the front as the Gulf Stream moved back and forth past the mooring. Very rapid and large changes in SST were observed that concurred with atmospheric conditions. Air-sea coupling such as wind intensification and cloud coverage is discussed. Comparison with NWP is also shown.