The evolution of a rain-produced, fresh surface anomaly observed in the western equatorial Pacific warm pool was modeled by use of the Princeton Ocean Model with Mellor-Yamada turbulent closure. The simulation was forced by a wind stress of 0.12 N m-2 and surface cooling of 225 W m-2. Following spin-up, 34-mm average rainfall was applied over a small portion of the domain. When rainfall ceased, momentum was trapped in a 1-m, fresh surface layer, and turbulent mixing was inhibited below the layer. Seven hours later, the surface density anomaly was reduced by an order of magnitude, and the surface velocity anomaly in the direction of the wind was 0.15 m s-1. The simulations show upwelling at the upwind edge of the anomaly and downwelling at the downwind edge with maxima of 15 and 35 m d-1, respectively. The momentum balance for the velocity component in the direction of the wind indicated that local acceleration, horizontal advection, and vertical diffusion were in approximate balance except at the downwind edge of the anomaly, where pressure gradient terms were also important. The budget of turbulent kinetic energy showed that shear production plus buoyancy production (or destruction) was approximately balanced by dissipation in much of the anomaly; advection and vertical turbulent transport terms were significant at some depths at the edges. The strength of the surface density front at the downwind edge of the anomaly tended to increase with time relative to the front at the upwind edge.