Promising prediction of the monsoon trough and its implication for tropical cyclone activity over the western North Pacific
The monsoon trough (MT) is generally recognized as a feeding ground for tropical cyclones (TCs) over the western North Pacific (WNP). In view of the many challenges that remain in current seasonal TC forecasting, it would be a profound benefit to understand the predictability of variations in the MT and the implications of this for the seasonal prediction of TC activity. This study reveals that high predictability of the MT is shown by the current atmosphere–ocean coupled forecasting system, with the correlation coefficient being 0.84 for the model-ensemble prediction with observations from 1960 to 2005. This high predictability arises mainly from the tropical dipole sea surface temperature over the Maritime Continent and tropical Pacific Ocean, which favors convection around the warm pool and further excites the vorticity anomalies over the WNP. It is further found that good knowledge of the MT could provide promising prediction of TC activity over the WNP, including the occurrence and energy of TCs. The findings of this study suggest that coupling between the WNP circulation and tropical ocean acts as an important source of seasonal predictability in the WNP, and highlight the importance of the MT for seasonal prediction of TCs over the WNP.