Evaluation of Capability of a Multi-model Ensemble System for Typhoon Forecast in Northwestern Pacific

One of the important tasks of Taiwan Typhoon and Flood Research Institute (TTFRI) is to conduct research on typhoon forecast, which is very important for disaster prevention and reduction, so TTFRI initiated Taiwan Cooperative Precipitation Ensemble Forecast Experiment (TAPEX) in 2010. Real-time 78-hour multi-model ensemble forecasts are run 4 times daily. The number of ensemble members was 20 in 2010 and 26 in 2015. Models used in TAPEX include Weather Research and Forecasting Model (WRF), Fifth-Generation Penn State/NCAR Mesoscale Model (MM5), Cloud-Resolving Storm Simulator (CReSS) and Hurricane Weather Research and Forecasting Model (HWRF). TAPEX performs well in typhoon forecast and the average typhoon track error reduces 26% from 2011 to 2014. The track errors for all typhoon cases in 2014 are 83, 138, and 208 km for 24, 48, and 72 hour forecast respectively. Evaluation of the performance of TAPEX in 2014 showed the ensemble spread with members of only one model is insufficient and the ensemble spread is slightly larger than the mean error if members of other models added, which means the choice of ensemble members is proper.