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Without getting too much into it, the PV is not like a surface storm or High. It doesn't have a range of movement or locations it goes over. It also doesn't have to move over a certain area to feel the affects of it. In fact it rarely enters the Eastern U.S as well.
Lets look at Seattle... December 2009. Look at that stretch of below normal temps first 2 weeks.. Lets look at the pattern that was in place...
All of these very cold days received almost no precipitation and they were probably clear. This is when we can get cold in the winter. This is why snow is very rare. 16-18F is the average cold it gets every winter and it happens when the sky is clear.
Good to have on file. Current location of the Polar Vortex is there. And note... it's 1 and strengthening. Not split and weak.
Also, Arctic Sea Ice affects the movement and location of it as well.
Lastly.. I think focusing on the PV is only to find the extremes or prolonged periods but yes, even knowing where it is can help figure out the patterns. I just don't think it's a big player until it weakens and splits.
All of these very cold days received almost no precipitation and they were probably clear. This is when we can get cold in the winter. This is why snow is very rare. 16-18F is the average cold it gets every winter and it happens when the sky is clear.
Cold source aloft is the reason as well. Top Down. You can have clear nights and it doesn't mean you'll drop to teens. It was very cold aloft.
If Pacific SSTs remain the same, LaNina east-based changes in atmosphere are likely in JAN/FEB.
Winters with an East-based Nina and a - QBO, we had colder Jan/Feb than December due to increased high latitude blocking that favored eastern 2/3 of U.S.
Without getting too much into it, the PV is not like a surface storm or High. It doesn't have a range of movement or locations it goes over. It also doesn't have to move over a certain area to feel the affects of it. In fact it rarely enters the Eastern U.S as well.
Lets look at Seattle... December 2009. Look at that stretch of below normal temps first 2 weeks.. Lets look at the pattern that was in place...
On December 6th, The Polar Vortex was still up near the Arctic, no where near the PacNW but because the Jet stream was dipping down Western U.S, over those tall Rocky mountains, cold air was coming down and there was an Upper Low over the Area.
Upper Lows generate cold periods.
but watch where that Polar Vortex went the following week..
December 10th it shifted south more and the PacNW had a very cold flow from the North thanks to a cold PV up there. Look at the lows that day
The PV made it to central Manitoba and started lifting north. Click source and go through the maps for following days
December 2008 was much more impressive for cold in the PNW. Dropped below -15C in Vancouver. Do you have a map for that event by chance? Would like to compare with Dec 2009.
It snowed 4.5" here last night. As far as I can tell, this is the earliest it's ever snowed this much here in history. It's beautiful with the fall leaves.
It snowed 4.5" here last night. As far as I can tell, this is the earliest it's ever snowed this much here in history. It's beautiful with the fall leaves.
I'm fairly certain you guys had snow on Nov 1st, 1984 and Oct 28th, 1991.
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