Arctic sea ice remains well below normal and possibly most importantly for longer-term weather, below normal sea ice anomalies have only become greater in extent in the Barents-Kara seas over the past few weeks. This also biases the winter forecast colder. Therefore based on above normal October snow cover extent across Eurasia, persistent below normal sea ice in the Barents Kara seas through the fall and early winter and the early tendency for high latitude blocking all favor a colder winter forecast for Northern Eurasia including Europe and East Asia and the eastern US, consistent with the winter forecast posted on the NSF website.
I also note that northern North Atlantic SSTs are warmer and shifted south compared to the same time last year. Northern North Atlantic SSTs for the past few winters have been exceptionally cold, which I believe favors an enhanced longitudinal temperature gradient, a strengthened Jet Stream, a positive NAO and a warm Europe. Potentially significantly warmer SSTs this winter could favor opposite conditions this upcoming winter with a weakened longitudinal temperature gradient, a weakened Jet Stream, a negative NAO and a colder Europe. And so far this fall, the NAO has had a negative tendency. But it is still very early and there are many other complicating factors still unknown. Even warmer SSTs are present in the northern North Pacific, which could also favor high latitude blocking this upcoming winter. But it is still very early and there are many other complicating factors still unknown. Also air and ocean temperatures remain near record levels across the NH and without dynamically forced cold (i.e., a weak polar vortex), the streak of warm weather will persist.
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