Awful news from Donny Sutherland in NYC thread.
Among those five cases, 2015 made a transition from predominantly negative AO values to predominantly positive ones during the fall. The combination of the AO's recent increase to the strongest positive values since April and some of the extended range guidance leave open a scenario where the AO is currently in the early stages of evolving to a predominantly positive regime. Such an outcome would also favor a warmer than normal fall and possible warm start to winter in the Middle Atlantic and southern New England regions. For now, this is merely a hypothetical discussion of one potential path toward winter. Many other variables are involved. The only idea that carries weight at this time is that the possible evolution reaffirms the longstanding signal for a warm fall.