I'm also really curious what driving force the seasonal dynamic models were seeing to make their +AO/NAO predictions.
On a larger note, a few years ago I saw some speculation that AGW would lead to a weaker polar jet thus more -NAO/AO episodes. The idea was that the strength of the polar jet is strongly affected by the latitudinal temperature gradient. As that gradient goes down with polar warming, the mean strength of the polar jet would also go down. It made sense to me. But obviously it didn't work out that way this year. Perhaps there is another forcing which is overwhelming it (maritime continent warm pool perhaps) or maybe it was just pure random chance. But the fact that the seasonal models picked up on it implies there is a non-random forcing element involved.