I've been watching Lingling and Dorian recently, and I'm interested that they both undergo extratropical transition and integrate their momentum into the jet stream around the same time:
Dorian and Lingling are the symmetrically opposite 968mb lows here. Their angular momentum seems to enhance a dipole pattern, and the timing of their momentum transfer will be critical to how it sets up here. Regardless of the exact configuration, it looks like this will split the initiating tropospheric polar vortex into two lobes and allow a major heat/moisture intrusion from the Pacific
As we enter peak hurricane season, it's important to remember that one of the major heat engines that moves heat from equator to pole are tropical cyclones, so watching their activity will be critical to see how the freezing season initiates (or fails to)
This to me indicates that the melting season is not over yet and way may see losses for the next two weeks. I would be stunned if the AO does not go negative again in the next two weeks, but then again I'm just a naive observer and not a pro meteorologist.
Edit: And after looking at this month's PIOMAS, I really wonder if this will push the Sept 15 update into first place.