Real-Time Forecasts of Typhoon Rapid Intensification in The North Western Pacific Basin with the NCEP Operational HWRF Model

ABSTRACT: This study presents the real-time performance of the United States (US) National Centers for Environmental Prediction (NCEP) operational Hurricane Weather Research and Forecast (HWRF) model in predicting rapid intensification (RI) of typhoons in the North Western Pacific (WPAC) basin in 2013. Examination of all RI cases in WPAC during 2013 shows that the HWRF model captures a consistent vortex structure at the onset of all RI as seen in previous idealized studies with HWRF. However, HWRF has issues with predicting RI when the model vortex is initialized with intensity greater than hurricane strength.Further verification of the probability of detection (POD) and the false alarm rate (FAR) of RI forecasts shows that the HWRF model outperforms all other models used by the US Navy’s Joint Typhoon Warning Center, possessing highest POD and lowest FAR in 2013. Examination of the intensity change forecasts at different forecast lead times also confirms that the HWRF model has superior performance, particularly at the 72-h lead time with the POD index ~0.91 and the FAR index ~0.33. Such unique performance of the HWRF model demonstrates its role in helping operational agencies improve their official intensity (and RI) forecasts for tropical cyclones in the WPAC basin. Keywords: rapid intensification, typhoons/tropical cyclones, operational forecasting