The surface coastal circulation in and off the Block Island Sound (BIS) is examined based on one- year HF radar (CODAR) observations, bottom-mounted Acoustic Doppler Current Profiler (ADCP) moorings, and a three-dimensional, primitive-equation model to characterize the buoyant flow patterns and their temporal evolution. Three analysis methods, visual sorting, Self-Organizing Maps (SOM) and Empirical Orthogonal Functions (EOF), are used and their results are compared. The Princeton Ocean Model (POM) is also applied to study the three-dimensional barotropic semidiurnal tidal response in the New York Bight (NYB) and Block Island Sound (BIS). This book represents the first comprehensive model and observation comparisons of the coastal buoyant outflows for an entire seasonal cycle. The success of this study is a major step towards developing a model-observational based coastal observatory system.