Variability of the observed midlatitude storm tracks in relation to low-frequency changes in the circulation pattern

Abstract The principal modes of month-to-month variability of the wintertime storm tracks over the North Pacific and North Atlantic are identified by empirical orthogonal function analysis of the root-mean-square statistics of bandpass (2.5–6 day) filtered geopotential height data for 19 yr. One of the two leading modes depicts fluctuations in the level of synoptic-scale activity without any noticeable spatial displacement of the storm track axes, whereas the other mode is associated with meridional shifts of the storm tracks from their time-averaged positions. Higher order modes are indicative of diversion or truncation of cyclone tracks in particular geographical regions. It is demonstrated that the leading storm track modes are linked to some of the best-known monthly averaged teleconnection patterns. The dipolar western Pacific and western Atlantic patterns for the monthly mean flow are seen to be accompanied by marked changes in the intensity of the storm tracks over the western oceans, whereas the m...