Interdecadal Variations in Northern Hemisphere Winter Storm Track Intensity

Abstract

Abstract In this paper, the interannual variations in the Northern Hemisphere winter storm tracks have been examined based on 51 winters (December–January–February) of NCEP–NCAR reanalysis data. The leading empirical orthogonal function (EOF) corresponds to the simultaneous strengthening/weakening of both the Pacific and Atlantic storm tracks. Interannual and month-to-month variations in the Pacific and Atlantic storm tracks are found to be significantly correlated. The principal component associated with the leading hemispheric EOF exhibits pronounced interdecadal variability. There appears to be a transition during the early 1970s from a weak storm track state prior to 1972/73 to a strong storm track state subsequently. Decadal mean storm track intensity during the 1990s is about 30% stronger than that during the late 1960s and early 1970s. The relationship between variations in storm track intensity and low-frequency (seasonal mean) flow anomalies has also been examined. It is shown that storm track va...