Behavior of sub-monthly wave patterns associated with recurving tropical cyclones during extreme intraseasonal phases in the western North Pacific

This study divided the sub-monthly cases into two intraseasonal categories: ISO easterly and westerly in the tropical Western North Pacific. In the westerly-phase ISO, the wave pattern was better organized and the TCs were clustered near cyclonic circulation of the wave pattern during the geneses, development, and propagation processes. However, the wave pattern and TCs were weak and poorly organized in the easterly phase. The distinct characteristics between the westerly and easterly phases could be attributed to ISO modulation on the monsoon trough and the subtropical anticyclonic ridge. The ISO enhanced monsoon trough in the westerly phase through strengthening the monsoon trough and increasing the moisture supply, while the ISO in the easterly phase blocked the moisture supply and thus provided a less favorable environment.