I mean technically everything is upstream of eachother since we're going around a spherical object....
But yeah, Tip is parsing the difference between what an index says and the "responsible party" for that pattern. I wasn't doing that....I'm merely stating that often a -NAO will be paired with a +PNA/-EPO type pattern, but when it isn't, it's really helpful to have. I'm not here to dispute that something in the PAC is causing that -NAO to occur....I'm just pointing out how helpful it is to occur during a shitty PAC pattern.
I've actually often stated that our best snow patterns are -PNA/-NAO/-EPO....kind of a weird trifecta on first glance, but think of something like Jan 2011 or Feb/Mar 2013. But obviously you can do the big snow thing other ways too....see 2015.