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Moving Through December - Changing Patterns and Changing Diapers


ChrisM

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The 11/27 event trended weaker because there was very weak baroclinicity with it. The shortwave became very strung out because there was no real potential energy for the storm to tap into. There was a weak, broad trough with relatively high heights and not a great thermal gradient. The fact that it trended weaker allowed for the east based -NAO to actually have an effect in pushing it east, along with a fact that a weaker shortwave won't amplify the downstream flow much.

This storm definitely has more amplification potential than the last event did.

Great post. On a global or broader scale, this storm is also the "momentum shift" type of an event where the Earth's exchange with angular momentum is locally restored after the recent +MT by the Rockies.

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Keep this month in mind. Boston climate December 2008:

I had mentioned that month a few times as an example of a see-saw/rollercoaster pattern that we ended up cashing in on despite the month finishing near +1. We had several 2-3 day torches that month.

But BOS finished with over 25" of snow. Over 30" back this way with an epic ice storm to go with it.

Its easy to miss out in a pattern like that too. You just need a few unpredictable factors to go against you, or go for you.

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Yea I think that would be the best possible outcome at least from a SNE non high elevation viewpoint, who wants a little icing then rain. Cut hard dry slot then some impressive squalls works for me.

Big storm will be nice looking on the water vapor loop though. Not Boring! lol

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I had mentioned that month a few times as an example of a see-saw/rollercoaster pattern that we ended up cashing in on despite the month finishing near +1. We had several 2-3 day torches that month.

But BOS finished with over 25" of snow. Over 30" back this way with an epic ice storm to go with it.

Its easy to miss out in a pattern like that too. You just need a few unpredictable factors to go against you, or go for you.

Yes you've mentioned that month and perhaps it's a good analog particularly factoring in November wx that year as well.

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Yes you've mentioned that month and perhaps it's a good analog particularly factoring in November wx that year as well.

I'd like to rebuild high heights over AK at some point later this month to feel good about a potential repeat of that fun period in '08.

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I'll be racking up my traces in no time!

Certainly exciting weather about to occur to our west. The usual "bleed east" wording seems in effect mid-month.

Seems that way.

I get the feeling I won't be doing much better in sw CT than you would be in central NJ in a gradient pattern. Dec 2008 was markedly better in this region than further sw, but that mid-dec wintry pattern for new england was driven by a stud -epo block, along side a -pna, +nao. The nao in the long range looks better than 2008, but the east pacific ridge does not look poleward enough to get me very excited. We shall see

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Great post. On a global or broader scale, this storm is also the "momentum shift" type of an event where the Earth's exchange with angular momentum is locally restored after the recent +MT by the Rockies.

I think that second shortwave coming through British Columbia by +150 hrs might be the most important contrary to the belief that the amplification of the first one is the make or break with that storm.

Either way we're now looking at the return of the polar vortex in a not-so-ideal position through Day 7. Lake cutters may help thump it around a bit but we will need strat and solar help too in order to completely dislodge it....MJO is 6 feet under now, too.The Euro weeklies were nice but I'm not sure how much stock I'm putting into them given their performance last run.

I think by the end of the month we'll be looking at a -PNA response..which will favor areas north with a bit of a developing gradient...where this sets up will be intersting to see (in terms of New England, not speaking about our area).

But I hate the Euro strat vortex forecasts now. The question moving forward becomes when are we going to see this vortex break down?

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You have to admit that this is slightly like last year where the GFS/EC would show a cold winter pattern in weeks 3-4 and then as we got closer to that time period they would warm and they would continue to repeat this over and over. I am not saying the warmth or alything else except the GFS/EC weeks 3-4 is like last year! just how they keep showing a good pattern in weeks 3-4 and then change it when that time comes around.

Yep nobody here wants to make that point yet and ultimately this IS different than last year as temps are not as warm. But so far we're getting the Charlie Brown syndrome again of the 2.5 to 4 week period looking good but never getting any closer.

I don't have the same hopes as everyone else. I just want to see things get more near normal but do expect we're going to be on the warmer side of even for quite some time. We'll have cold periods and threats this year for sure.

It'll take another 2 weeks of the pattern change being 3 weeks away before we will see a mass realization. A couple of weeks ago people were saying the first week or two would be cold and we'd flip to warm by Xmas. Now we're warm and hoping to flip to cold by Xmas :(

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I think that second shortwave coming through British Columbia by +150 hrs might be the most important contrary to the belief that the amplification of the first one is the make or break with that storm.

Either way we're now looking at the return of the polar vortex in a not-so-ideal position through Day 7. Lake cutters may help thump it around a bit but we will need strat and solar help too in order to completely dislodge it....MJO is 6 feet under now, too.The Euro weeklies were nice but I'm not sure how much stock I'm putting into them given their performance last run.

I think by the end of the month we'll be looking at a -PNA response..which will favor areas north with a bit of a developing gradient...where this sets up will be intersting to see (in terms of New England, not speaking about our area).

But I hate the Euro strat vortex forecasts now. The question moving forward becomes when are we going to see this vortex break down?

Yeah, the MJO completely dying in combination with the 11/27 event not becoming a wave breaker for the -NAO formation really messed things up. That might have been our best change to dislodge the pattern to our favor, until late December, anyway.

I'm skeptical of the Euro weeklies because I don't see a driving mechanism to force a west based -NAO. Wave breakers can only do so much with the stratospheric vortex so awful and the MJO essentially dead. MJO phase 1 also correlates to positive height anomalies over Greenland, too; it's not just a +PNA/Aleutian low thing.

Given weak ENSO state and not strong influence from the Atlantic, the primary pattern forcing will come from the Pacific and the vortex. Both of which look pretty bad.

New England can still do okay from the Aleutian Ridge and temporary Atlantic ridging, forcing a strong thermal gradient/boundary for storms. But us? Meh.

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I know many are concerned with the stratosphere and reasonably so, but you can get periods of tropospheric induced -NAOs. You don't always need a lake cutter to throw a ridge into the Davis Straits either...a nice Aleutian or even AK ridge can help teleconnect to one. Of course it probably would mean more transient and/or east based -NAOs...but just something to remember.

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Yeah that is oozing low level cold there.

Yeah, despite the very amplified look, shortwaves and areas of vorticity run through Quebec and Ontario, creating a confluent zone, which creates a nice surface high and further enhances the thermal gradient.

The gradient is so strong over so much area that precip can run well out ahead of the storm. So even if the main storm ultimately takes a pretty far westward track, an ice event could still occur since precip can overspread the region when it's still cold in New England and when the storm is well to the south. How much precip works its way northeastward in advance of the storm will be important.

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Yeah, despite the very amplified look, shortwaves and areas of vorticity run through Quebec and Ontario, creating a confluent zone, which creates a nice surface high and further enhances the thermal gradient.

The gradient is so strong over so much area that precip can run well out ahead of the storm. So even if the storm ultimately takes a pretty far westward track, an ice event could still occur.

Yeah the GFS has been doing that for a few runs, while the euro is further west and more amped up with the CONUS trough..and less confluence over Canada. That's why I thought the interior could start as ice, but I couldn't really say much more 7 days out.

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