Some thoughts....

Some additional thoughts on this winter's outlook... Last winter as most of us recall, featured rather warm temperatures. This was in part due to the lack of cold air in Canada (it was also a rather warm year in western and Central Canada), and the fact that there was virtually no atmospheric blocking across the North Atlantic. Towards the latter half of the winter season, an SSW occurred over the Arctic regions. An SSW stands for Sudden Stratospheric Warming event. In theory, an SSW should lead to increased atmospheric blocking over the North Atlantic or the Arctic, approximately 2-4 weeks after the SSW has occurred. Last winter, it came too late, as very little extremely cold air had built up over western and central Canada. When conditions were favorable over Alaska for the build-up of a record breaking cold air mass, the jet stream patterns became unfavorable for the movement of this arctic air mass into the Eastern United States. This year, over the course of the spring and summer months, strong atmospheric blocking has set up across the North Atlantic. In fact, we just recorded the lowest NAO value on record back in June (Climate Prediction Center).. Right now, positive stratospheric temperature anomalies have been building across the North Pacific and Arctic regions, possibly in correlation with the strengthening negative PDO regime. This has lead to a drastic drop in NAO values over the past week or so, and the reason for the cooler weather. IF this pattern can stay in place for the next couple of months, it could possibly become the main winter weather pattern. This kind of a pattern would be very favorable for extremely cold winter weather, but drier conditions across the Northern U.S. Another signal I'm looking at is the ENSO conditions. If the CFSv2 long range forecast is correct (the first set of ensemble members), then the El Nino will weaken considerably by December, and become neutral. This remains consistent with the fact that El Nino's usually struggle to develop in the negative episode of the PDO. Of course I am still investigating this winter, and I will provide more updates as the week goes on, but at this point, there are three possible weather patterns that this winter COULD feature: One, a rather warm, and possibly wet winter associated with the El Nino (similar to 2006-2007). Two, a rather cold and dry winter, similar to the winter of 93-94. And three, a winter similar to 2010-2011 where the negative PDO, intense atmospheric blocking, and positive PNA patterns dominated and caused a rather cold and snowy winter. The most likely winter weather pattern at this point is number one, mainly based on historical analogues. After reviewing the data, this year is very unique in the fact that virtually no years in the historical record from 1951 onward even come close to having similar weather conditions to this summer and fall. This may be a rather unique winter season, and quite a bit different from the last winter season. I will discuss this in a related post tomorrow.

All in all, the most likely scenario for the winter is one that features near or slightly above normal temperatures, and likely above normal precipitation (given a strong southern jet stream, which will average farther north than normal)..