A monitoring mission to study the shape and estimate initial dilution of the S. Jacinto outfall plume using an Autonomous Underwater Vehicle was performed on July 30, 2002. In order to reduce the uncertainty about plume location and concentrate the vehicle mission only in the hydrodynamic mixing zone, outputs of a near-field prediction model, based on effective real-time in situ measurements of current speed and direction and density stratification, were opportunistically used to specify in real time the mission transects. The surface characteristics of the outfall plume were found to be...