Regional modelling of the western Pacific typhoon season 2004

An ensemble of typhoon events was examined to detect systematic skills and deficiencies of regional atmospheric models in dynamical downscaling these extreme weather phenomena from global reanalyses data. A regional atmospheric model hindcast was computed for the typhoon season 2004 for SE Asia and the western North Pacific. Global reanalyses data were dynamically downscaled to a grid resolution of about 50 km and in a double-nesting approach to 18 km. Simulated typhoon tracks and intensities were compared to best track data. The comparison revealed improved SLP and near-surface wind values by the RCM compared to the reanalyses for most cases. The reanalyses showed smaller great circle distances to the best track data than the regional model. Precipitation patterns and rainfall amounts were simulated more realistically by the RCM using the higher resolution compared to the 50 km run. It is concluded that regional models can improve simulated typhoon developments from global forcing reanalyses data by giving lower core pressure and higher wind speeds and more realistic precipitation patterns even though these values still do not reach observed values