Book excerpt: A previously calibrated numerical three-dimensional hydrodynamic model for Los Angeles-Long Beach Harbors, California, was applied to study the combined effects of tide and wind on circulation. The model was calibrated and verified successfully with field data for a summer wind condition. In this report the calibration is compared to a no-wind condition to understand the effects of typical wind conditions on circulation. Also, wind conditions for approaching (winds from the southeast) and passing (winds from the north) frontal systems, typical of fall-winter weather patterns, were simulated. Results indicated the effects of wind can be significant. Harbors, Long Beach Harbor, Wind-driven circulation. Hydrodynamics, Numerical models, Los Angeles Harbor, Tidal circulation.