From 2007-2013 we had a pretty sustained negative PDO with only a brief positive period during the el nino of 2009/10. Then we had a positive phase for 50 months, from 2014 through March 2018. This summer its been pretty flat and oscillating near zero. Interesting that even during pretty much the entire la nina we maintained a +PDO and only now are seeing some negative months as the next el nino sets in. Hard to say if the somewhat negative PDO look is the result of a few years of la nina trying to erase the mega +PDO and will disappear as el nino builds or if there is actually something driving the -PDO in spite of the developing el nino. Any ideas?
I'd venture that 2002 looked -PDO going into winter because of the 3 year la nina event preceding it, but that look disappeared heading into winter as el nino grew. In some sense we could be in a similar boat here and I wouldn't be shocked to see the -PDO disappear in the next 1-2 months. At least for now though, the waters off of Japan are warming and near the west coast they are cooling.