Warm and cool phases of the PDO can persist for decades, usually about 20 to 30 years. A warm phase occurred from 1925 to 1946, a cool phase from 1947 to 1976, and then another warm phase from 1977 to 1998. Currently, the Pacific Ocean is in a cool PDO phase that began around the turn of the century and the recent years of 2008 and 2012 actually exhibited the most negative PDO index values since the 1950’s.

Graph at link:

[link to thesiweather.com]