Large-scale flow reconfigurations over North America associated with recurving western North Pacific tropical cyclones

Recurving tropical cyclones (TCs) can sometimes lead to reconfigurations of the extratropical large-scale flow well downstream of their point of recurvature. Previous case studies have suggested that recurving western North Pacific (WNP) TCs can remotely alter the large-scale flow pattern over North America via two main pathways: (i) by strengthening and elongating the North Pacific jet stream, thereby leading to eastern North Pacific cyclogenesis in the poleward jet exit region and associated western North American ridge development, and (ii) by exciting or amplifying a Rossby wave train along the North Pacific jet stream, resulting in a wave-like flow pattern over North America. The present study builds upon previous case studies by using composite analyses to investigate various pathways to North American large-scale flow reconfigurations associated with recurving WNP TCs.

Episodes of 1979–2009 recurving WNP TCs are grouped for compositing based upon the evolution of the North Pacific jet stream and the large-scale flow pattern over North America during and following TC recurvature. Composite analyses constructed from 2.5° NCEP–NCAR reanalysis data are used to identify synoptic–dynamic characteristics associated with various North American large-scale flow reconfigurations following WNP TC recurvatures. Preliminary results indicate that North American large-scale flow reconfigurations associated with jet stream intensification and elongation tend to be preceded by anticyclonic wave breaking over the North Pacific. In contrast, North American large-scale flow reconfigurations associated with Rossby wave train excitation or amplification tend to be preceded by cyclonic wave breaking over the North Pacific.