Followup Notes: With only a few weeks of meteorological fall left, I continue to wonder about the -EPO and how it may be a saving grace for the Tennessee Valley this winter. With the QBO in a positive and falling state, I expect the polar vortex to start out strong but weaken as we approach winter, which is part of the reason I expect the second half of winter to be stronger and more intense than the first half. Since the AO/NAO is partly tied to the QBO, and since a +QBO would likely lead to a +AO/+NAO, I can definitely see warmer than normal temperatures to abound in December for the third consecutive year, with each subsequent month lessening in terms of positive temperature anomaly; however, with a strong -EPO, the pacific pattern allows troughing to dig into the southeast quadrant. My guess at this point is we could see a winter, temperature wise, similar to 2007-08. During this winter, December was a torchfest, but January evened out and February and early March featured some memorable snow events. I will note that we near the launch of Yuletide, December is looking more and more like a coin toss.
From this animation, you can clearly see how the two blocks develop, ‘wobble’ and then trap the cold air in between. When this happens, the cold air is essentially channeled southward towards the Lower 48. Early indications reveal the trending -NAO pattern appears east based, though this doesn’t mean the –NAO will remain that way.
Note: EPO graphic from DT Wxrisk. Check out his Thanksgiving video here:
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