Predictability associated with interactions between recurving West Pacific tropical cyclones and the extratropical large-scale flow

Interactions between recurving West Pacific tropical cyclones (TCs) and the extratropical large-scale flow can yield major changes in Northern Hemisphere (NH) jet stream structure and Rossby wave patterns. Such circulation changes sometimes can result in high-impact weather events and a subsequent period of reduced predictability over the Pacific Ocean and North America. Thus, an important scientific issue is to identify what characteristics distinguish TC/large-scale flow interactions that produce major circulation changes from those that do not. In this presentation, this issue is addressed by applying quasigeostrophic and potential vorticity diagnostics to recent cases of recurving West Pacific TCs. Preliminary results indicate that the ability of a recurving West Pacific TC to produce a substantial, persistent reduction in predictability may depend upon whether a Rossby wave train is excited by the TC/large-scale flow interaction. These results also suggest that a Rossby wave train may be more likely to be initiated by the TC/large-scale flow interaction, and predictability to be reduced, when cyclonic rather than anticylonic wave breaking is induced by the interaction.