We need a -AO and or -EPO to deliver legit cold. Outside of that we rely on a dynamic system(evap/dynamic cooling) with a very favorable track, and probably need a significant, established negative NAO to feed cold enough air southward as a coastal low climbs the coast. That's kind of always been part of the formula, esp in a Nino, but might be a bit more of a challenge today. Thus why I generally don't mind Ninas at all lately given my location, mostly depending on the NE Pac ridge position/orientation.