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LR THREAD: Next 7+ days will be rather benign, but I'm confident this will change not only to colder temps than this week, but also colder than average, and a more active precip pattern. Attached is an image of expected 500mb height anomalies on the GEFS on 1/23 at 7:00pm (1/X)
Yes, the GEFS is a model projection (blended 30 members) but there are observational things on the other side of the globe that make this look legit. As shown, it is suggesting a -NAO, -AO, slightly -EPO, -PNA. Right now the Pacific Jet is killing us...+EPO and mild temps (2/X)
So how do we get rid of the Pacific Jet extension? First, we need to discern how it got there in the first place. The image here is a positive East Asian Mountain Torque (+EAMT) in early Jan. This created an accelerated flow off the Himalayas, and led to the jet extension (3/X)
This is now flipping, and the EAMT is turning negative. This will effectively shut off that accelerated Himalayan flow, and the Pacific jet is less effective/less influential. Shown is the loop of the 300mb jet breaking down around the 18th or so... (4/X)
Everything has a downstream effect...one begets the next...when the Pacific jet weakens, the persistent Gulf of Alaska low that gave us a +EPO and milder temps, especially this week, will break down with the jet, and ridging enters into Alaska in its place as shown: (5/X)
This leads to changes to our pattern and more active in the 2 week period between the last 10 days of Jan through the first several days of Feb. Snow chances come into play at that time. Until then, it will remain relatively benign. This was our target date. Still good (6/X)
Lastly, a turn milder is possible for about two weeks in February. This is also due to the EAMT turning positive again, accelerating the PAC jet and combining with Maritime Continent tropical forcing to produce mild temps. Think it may turn colder again late Feb into March (/end)
