Interactions between recurving west Pacific tropical cyclones and the extratropical large-scale flow

Interaction between a recurving West Pacific tropical cyclone (TC) and the extratropical large-scale flow can yield major changes in Northern Hemisphere (NH) jet structure and Rossby wave patterns. Such circulation changes can sometimes 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, we address this issue by applying quasigeostrophic diagnostics to four recent cases of recurving West Pacific TCs.

The four recurving West Pacific TCs chosen for study are Typhoon (TY) David (1997), TY Opal (1997), TY Songda (2005), and Tropical Storm (TS) Haima (2005). Case studies of TY David and TY Opal are conducted in order to continue previous research by Harr and Elsberry on frontogenesis patterns associated with the recurvature of these two TCs. Case studies of TS Haima and TY Songda are chosen so that characteristics of a recurving TC yielding a relatively large downstream circulation impact (TS Haima) can be contrasted with a recurving TC yielding a relatively small downstream circulation impact (TY Songda).

Preliminary results indicate that the ability of a recurving West Pacific TC to produce a substantial reduction in predictability may depend upon whether a Rossby wave train is excited by the TC/large-scale flow interaction. Results also indicate 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.