Let's start off with the North Atlantic Oscillation or NAO. In the winter, a negative NAO means there is a better chance for cold and storminess along the East Coast. As you can see, it's been a while since the NAO has been negative. In fact, the NAO is going to spike positive through the end of the month, but the red line which is showing the model forecasts is hinting for a change by the start of December.
Now let's look at the Arctic Oscillation. A positive Arctic Oscillation usually means that the cold is locked up more toward the pole. However, warming aloft results in a negative AO which then helps to push cold air southward away from the poles. Once again you can see the trend coming, but not for a while. But the models are indicating a crash toward early December which matches to what I think will be a push to some significant cold coming our way next month.
Now let's look at the Pacific/North American Pattern. A negative PNA usually means a trough in the west with cold and unsettled weather out there. A positive PNA means a ridge in the west and promotes a trough with cold in the east. As you can see below the PNA is negative but will be switching to a positive sharply at the end of the month.
The long range models are mixed. The European model is showing the cold starting to push at the end of the long holiday weekend. This model is one that has a lot of my faith in the winter months and has been doing quite well, but the indices and my past experiences tell me that it may be rushing in a little fast. Though take a look at the GFS model for early December. Some serious cold pushing our way.
