In the present paper we propose an improved Nihoul's model which accounts for the main forces acting on an oil slick and ruling its spreading and transport in the first tens of hours after the spill. In the original model, Nihoul considered the Coriolis force to be negligible; we re-formulate Nihoul's analysis including the Coriolis force in the mathematical model. Coriolis force is found to act on both the oil slick transport and spreading processes in a non-trivial way and depends on several parameters. We numerically assess the importance of the Coriolis force on oil slick transport at different latitudes and spill conditions. Simulations carried out considering different model conditions show that the use of empirical parametrizations of the drift angle, when applied together with hydrodynamic models, leads to incorrect prediction of the slick trajectory. Finally we propose an empirical, simplified formulation which describes the trajectory of the oil slick's centre of mass considering the Coriolis deviation.
