The Curimataú River estuary is a shallow partially mixed (type 2) tropical estuary, located in the Rio Grande do Norte (RN) state, northeast Brazilian coast (lat. 06o18’S); the main system is composed by three rivers: Curimataú, Cunhaú and Guaratuba. The numerical model Delft3D-Flow was used to study hydrodynamic features of the estuary. The model predictions were evaluated using the Skill parameter based in the comparison of the theoretical solutions with observations of hourly values of tidal heights, currents and salinity at an anchor station located at the cell (M=279; N=323). The applied computational grid is curvilinear with around 6,000 horizontal wet points, including the inner shelf. Open boundary conditions was obtained from the analysis of 2.7 years of hourly tidal heights, recorded at Natal harbor, and the inner boundaries conditions were controlled by freshwater input into the three main rivers. Initial conditions of hydrographic properties were uniform in the previous simulations and, only the temperature was set to a constant value in whole simulation. The steady-state of the fields of velocity and thermohaline properties was reached after almost four weeks of simulation of the baroclinic mode. The best fit between the model and the observations was for the semidiurnal spring tide oscillation with a Skill=0.98; for the velocities and salinities simulations during this tidal condition the best mean Skills values were 0.82 and 0.94, respectively
