FORECAST AND HINDCAST SIMULATIONS OF THE BRAER OIL-SPILL

Model predictions of the movement of oil released during the Shetlands oil spill in January 1993 commenced immediately following the grounding of the Braer. The initial forecasts, made with a 5 nautical mile grid model, predicted oil along the west coast of the island but were too coarse to resolve the coastal bathymetry and circulation. This forced the development of a fine grid (924 m) hydrodynamic model of the region which was interfaced to surface wind forecasts and meshed to a shelf-wide storm surge model. Into this detailed model were merged particle tracking algorithms to simulate the movement and spreading of the oil. This model development required intensive efforts in the days following the spill. Some of the early predictions were in error, in part due to the complexity of the task and in part due to the lack of observational results to confirm the movement of the oil. However, hindcast simulations made in the montbs following the accident probably present a realistic account of the movement and spread of the oil. The hindcasts correctly simulate the presence of oil on the sea bed 100 km to the south of the spill site. This was an unexpected feature of the oil trajectory and its simulation has given additional insights into the dynamical processes that can influence the movement of oil.