This paper approaches the problem of output power prediction for an off-shore wind park. To this end, a so called wind deficiency factor for each turbine and for each wind direction sector is identified using past data. This identification is done by using the effective wind speed concept that can establish a link between output power of each wind turbine and meteorological mast measures in terms of wind speed and direction. Based on forecast wind speed and direction, a wind park simulator that uses the previously identified deficiency factors, computes future output power time evolutions. Nunierical simulations show the feasibility of the proposed approach. (C) 2016 Elsevier Ltd. All rights reserved.