Tropical cyclones (TCs) can have large impacts over land and marginal seas in the western North Pacific (WNP), especially in the Southeast Asia (SEA) region where countries, such as the Philippines and Vietnam, are among the most exposed in the world to TC-related hazards. Each year there are over 20 TCs on average affecting SEA, with about 50% of them occurring in the peak-season of July-September (JAS), where the TC season is usually defined as June-November. Accurate prediction of peak-season SEA TCs up to several months ahead can provide an early warning service, which may significantly reduce the damage from TCs to economic activity and social welfare.Dynamical general circulation models (GCMs) have been developed as a useful tool for seasonal TC prediction, especially in recent years with the development of high-resolution climate models related to the rapidly increased computing capability. Dynamical seasonal forecast systems have been developed in the major meteorological