Abstract -- Mesoscale models have been widely exploited in short-range forecasts over the world in recent years. In Taiwan, MM5 is adapted as a forecast model in the Central Weather Bureau (CWB), in addition to its Limited-area forecast System (LFS) that is based on the Navy model. Therefore, it now becomes very important to assess the ability of MM5 in rainfall forecasts in the Taiwan area. In this study, we examine the performance in terms of rainfall forecast of a 5km MM5 that was run in the CWB during the 2001 Mei-yu season. We also compared the result with the 15km MM5 in order to explore the impact of increasing model resolution in rainfall forecast.
The verification results show that the model performance in rainfall forecast does improve slightly by increasing the model resolution from 15 km to 5km. The progress is larger for medium and heavy rainfall thresholds (>15 mm). The ETS decreases when the rainfall thresholds increase or the forecast length extends longer.