The El Nino last Winter matched the El Nino/-PDO blend over N. America just about perfectly. I always think SSTs are secondary, but according to some sources, there are anomalies up to +15F in that PDO region! Put hot bath water in a room, and you'll raise the temperature 0.1-0.2 degrees. It's also a matter of consistency forecasting, since we don't always know everything, and similar global factors occurring are more likely to repeat.
Yeah, there's obviously a relationship between ENSO and PDO, yet they also have some separate characteristics.
We are in one of the deepest -PDO periods on record, yet we're coming out of a major Nino and just entering a very weak Nina.