In recognizing the indigenous wind energy resources in the Korean peninsular and offshore regions, and wind energy as practical, feasible and beneficial for augmenting economical development in South Korea, the Korean government and several heavy industries in the country actively promote, invest and rapidly develop wind energy generation. To support the Korean wind energy development, especially for supporting wind power grid-integration and wind farm operations, the National Institute of Meteorological Research of Korean Meteorological Administration and the National Center for Atmospheric Research are jointly developing a wind modeling system based on the NCAR WRF and MM5 based Real-Time Four-Dimensional Data Assimilation (RTFDDA) and forecasting system. The ultimate goal of this project is to advance, tune-up and customize a suite of WRF-based modeling technologies developed at NCAR, including the operational capability of multi-scale 4DDA and forecasting with ultra-fine LES-scale grids covering major wind farms in Korea, multi-perturbation-approach, multi-model mesoscale ensemble probabilistic forecasting, advanced model output statistical bias and probability calibration, micro-climatology modeling technology for supporting guidance to wind farm and wind turbine, and real-time weather forecasts for supporting wind farm operations. In this presentation, we will first summarize the proposed modeling technologies and a plan toward the NCAR next-generation 4D-REKF (4 dimensional relaxation ensemble Kalman filter) based, integrated ensemble data assimilation and ensemble prediction system for optimizing regional and wind farm wind forecasting. Then we describe the first-phase WRF-RTFDDA based multi-grid mesoscale and LES-scale forecasting systems implemented for the Korean peninsular. We will report the preliminary evaluation of the system with case studies for several cases. Comparison study with simulations with mesoscale grids versus LES-scale grids will be discussed. Impact of the data assimilation with the regional weather data, the dense Korean Automated Weather Observation System (AWOS) network, and the wind farm weather and wind measurements, on the wind forecast will be reported.