Following the growth of wind sector and the scarcity of available land, the market share of onshore wind energy installation on complex terrain is expected to increase. Wind resource assessment is a crucial process for the successful development of a wind farm project. To estimate the future energy production on a specific site, developers investigate the potential wind power which is related to the local winds. For cases of complex terrain with significant changes in roughness due to vegetation or buildings, local winds can vary considerably across a wind farm site, resulting in inaccurate energy estimation. The site under investigation is on an island of complex terrain covered by 70% of thick forest and trees of roughly 15 to 20 m height. The atmospheric boundary layer stability is mainly neutral with a very unidirectional wind direction from ESE. Two meteorological masts have been installed providing measurements of more than a year. Average wind speeds over the NW direction and at 78 m height were measured to be 2.698 m/s for the first met mast and 2.545 m/s for the second met mast respectively. A wind resource assessment has been performed using 12 wind sectors and the commercial software MeteodynWT. At the current poster, preliminary results using computational fluid dynamics (CFD) simulations of the steady state 3-D Reynolds-Averaged Navier Stokes (RANS) equations with the open-source CFD software OpenFOAM are compared to the met masts measurements.