The mechanisms of interannual variability within the North Pacific storm track

The processes and mechanisms controlling variability of the Pacific storm track have long been a topic of interest in atmospheric sciences. Recent work using feature-tracking techniques has shown that seasonal variability, in particular the midwinter minimum, can be explained by there being fewer, smaller amplitude disturbances that enter the Pacific storm track from mid-latitude Asia, rather than any unusual atmospheric dynamics within the storm track itself. We extend this analysis to explore the causes of interannual variability of the wintertime Pacific storm track. This work reveals that, in direct contrast to the seasonal cycle, interannual variability is dominated by local dynamical processes. In particular, we find that for winters characterized by a strong, narrow jet stream, the individual disturbances that comprise the storm track are weaker than normal, and vice versa for winters with a weak, wide jet stream. Further investigation reveals a connection between the observed interannual variability of the Pacific jet stream and the relative importance of “LC1/anticyclonic” and “LC2/cyclonic” storms. Finally, the implications of these results as well as the important differences between observed patterns of Pacific storm track variability are discussed.