Starting about October 9th, there is a real nice signal for +PNA from 18z GFS ensembles
http://www.meteo.psu.edu/ewall/ENSHGTAVGNH_18z/ensloopmref.html
This is, as ENSO subsurface is starting to warm rapidly
https://ibb.co/1nrDtgp
(I have in the past correlated ENSO subsurface conditions with + and - phases of the PNA in 0-time. The +PNA being show on 18z GFS ensembles days 12-15 is broad and deep, would reflect some stronger ENSO coupling to the N. Pacific pattern, and possible subsurface strengthening.)