The North Pacific Oscillation (NPO) in sea-level pressure and its upper-air geopotential height signature, the West Pacific (WP) teleconnection pattern, comprise a prominent mode of winter midlatitude variability, the NPO/WP. Its mature-phase expression is identified from principal component analysis of monthly sea-level pressure variability; as the second leading mode, just behind the Pacific-North American variability pattern.

NPO/WP variability, primarily on subseasonal time scales, is characterized by a large-scale meridional dipole in SLP and geopotential height over the Pacific, and linked to meridional movements of the Asian-Pacific jet and Pacific stormtrack modulation. The hemispheric height anomalies at upper levels resemble the climatological stationary wave pattern attributed to transient eddy forcing. The NPO/WP divergent circulation is thermal-wind restoring, pointing to independent forcing of jet fluctuations.

Intercomparison of sea-level pressure, geopotential height, and zonal wind anomaly structure reveals that NPO/WP is a basin analog of the NAO; not surprising given strong links to stormtrack variability in both cases.

The NPO/WP variability is influential: Its impact on Alaskan, Pacific Northwest, Canadian and US winter surface air temperatures is substantial; more than PNA or ENSO's. It is likewise more influential on Pacific Northwest, western Mexico and south-central Great Plains winter precipitation.

And finally, and perhaps, most importantly, NPO/WP is strongly linked to marginal ice zone variability of the Arctic Seas; with an influence that surpasses that of other Pacific modes. Although, NPO/WP variability and impacts have not been as extensively analyzed as its Pacific cousins' (PNA, ENSO), it is shown to be more consequential for Arctic sea ice and North American winter hydroclimate.