December 2020 Medium/Long Term Pattern Discussion.

[John1122]

Some years we get stuck in a pattern and models try to get out of them, but they just stay in place as we get to reality. Granted, 80 percent of the time the pattern seems to lock in never ending warmth. But a few years it locks and repeats cold like 95-96, 09-10, 10-11, 14-15, 15-16 etc.  Usually once those patterns finally do break we get a long term swing in the opposite direction. Unfortunately for us, the last several locked in long term repeating warmth patterns lasted until basically the start of Met spring and we just had cold. wet, miserable spring seasons. In the years where cold repeated, usually by mid February it lifted out and we torched for weeks on end. It seems like one of those years summer basically started in late April and never let up.

[Holston_River_Rambler]

Still a looooong ways to go, but there may be some over performance potential with this set up:

 

 

[Holston_River_Rambler]

RGEM looks even more interesting, if more marginal:

 

 

 

 

 

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[nrgjeff]

First, I always approve of severe wx jawboning messages, lol. ECMWF weeklies do warm up the back half of December. MJO over the Maritime Continent is southwest flow aloft if a shortwave and airmass can come together. Still a few weeks off so I've nothing to add there. 

Speaking of the MJO it is weak. However I always prefer it in cold phases than warm, no matter the strength. While the plot is Maritime Continent, the West Pac tries to flare up too. Explains how we're getting this couple weeks of cool volatility instead of blast furnace.

Looking way ahead in years with La Nina atmospheric response and -GLAMM which is all forecast the next few weeks, the warm back half of December does not necessarily have to last. Some of those years with a cold start to December, and warm finish, went on to get cold again in January. About half the years went cold January. Now, if this late December warm busts, and it just stays cold, that's not bad either. Talking snow perspective here. 

My gut says this winter will be more interesting than that last few, with more bouts of snow. Confidence is increasing in the La Nina with -GLAMM response. That's variable vs locked in SER, but we will have warm days. Should get occasional cold air delivery. Cheers!

[Holston_River_Rambler]

Speaking of interesting. 18z Euro handles the energy early next week interestingly:

 

[Carvers Gap]

1 hour ago, Holston_River_Rambler said:

Speaking of interesting. 18z Euro handles the energy early next week interestingly:

 

Good find.  Nice snow at the surface in SW VA which is a BIG change.  Was fairly benign until that run.

[Holston_River_Rambler]

A met in the MA forum mentioned the UKMET overnight, so guess what I did as soon as I saw that, lol, like a moth to a candle:

 

One thing I'm interested in this AM is the RGEM. Unless I have missed something it is, very nearly,  on a an island in how it handles the three pieces of energy. It misses the phase between the what I'm calling energy piece #2 (circled in pink) and #1 ( circled in black). 

6z Euro for comparison:

6z Euro 3 hour precip:

 

To misquote Wellington, "it's a damn close-run thing."

UKMET, NAM 12km, and even the RGEM's parent, the CMC also have that capture. Interestingly the 6z GFS doesn't. 

As volatile as things have been, I'm hesitant to say there's pretty good agreement for some sort of wintery weather in eastern areas of our forum, but definitely still intriguing this AM.

 

 

 

 

[Carvers Gap]

22 minutes ago, Holston_River_Rambler said:

A met in the MA forum mentioned the UKMET overnight, so guess what I did as soon as I saw that, lol, like a moth to a candle:

 

One thing I'm interested in this AM is the RGEM. Unless I have missed something it is, very nearly,  on a an island in how it handles the three pieces of energy. It misses the phase between the what I'm calling energy piece #2 (circled in pink) and #1 ( circled in black). 

6z Euro for comparison:

6z Euro 3 hour precip:

 

To misquote Wellington, "it's a damn close-run thing."

UKMET, NAM 12km, and even the RGEM's parent, the CMC also have that capture. Interestingly the 6z GFS doesn't. 

As volatile as things have been, I'm hesitant to say there's pretty good agreement for some sort of wintery weather in eastern areas of our forum, but definitely still intriguing this AM.

 

 

 

 

Interesting for sure and a great share.  Looks like the 6z off-run of the Euro is slightly SE of 0z.  Wonder if the models which over-amped the last storm are doing the same with this one?  I bet the solution is somewhere in between the Euro/UKMET and GFS.  Probably not good for us as that would shift the phase eastward, but probably less benign than the GFS.

[Carvers Gap]

After next week, looks like the current cooler pattern will relax or change to a new pattern from say Dec 18-Jan7.  The CFSv2 implies that the trough will return early in the new year as does the GEFS extended.  The GEFS holds a -AO/-NAO couplet.  The GEPS/EPS lose the Pacific.  The American model suites tend to have an Atlantic driven pattern - that would be unusual per the last decade's results and should be viewed with some healthy skepticism - but not discounted.  The warm pool in the northern Pacific is making it tough for troughs to hold there IMO.  In the days (prior to winter disappearing after early Dec), we would call what is upcoming a "thaw," and would be a very normal time frame for that to happen.  So, looks like the second week in January is the fork in the road.  If we are going to have winter return, looks like that is the time - and by "return" I just mean a healthy pattern where things oscillate between warm and cold (I don't think we lock into a cold pattern this winter for more than 10 days or so).  

[John1122]

The EPS is a worst case scenario. The polar vortex heads to Alaska in about 2 weeks.  That tends toward being a stubborn pattern to dislodge. Have to hope it doesn't happen at all. 

[Daniel Boone]

8 minutes ago, John1122 said:

The EPS is a worst case scenario. The polar vortex heads to Alaska in about 2 weeks.  That tends toward being a stubborn pattern to dislodge. Have to hope it doesn't happen at all. 

Yeah, for sure John. Still some hope for last nights depiction to be possible, with enough NA blocking and that NE PAC warm pool as Carver aluded to.  But, with the Nina, in particular it's strength, this new depiction has greater odds of happening i.m.o, unfortunately .

      Maybe, it'll be more back and forth between the 2. If so, we can work with that.

[John1122]

EPS was night and day different 12z to 00z.  It went from a deep Alaska vortex at D 14 to a PNA ridge, -NAO look and a deep Eastern trough. 

[Holston_River_Rambler]

Thought I'd do a little poking around the strat this AM. 0z 6z GFS almost, kinda, sort of tried to do a little split in about ten days:

0z run:

6z

 

To be realistic, 10 - 14 days is waaaayyy out there, even for something as simple as trough and ridge location and even more for anything happening to the strat. Even if it did split, there are a lot of ways that could go wrong.  Something to watch anyway.

On a related note, looking at GFS's depictions of the dynamic tropopause and vorticity way up in the atmosphere, this attempt at a split may be tied to two things, on different sides of the globe. Over Siberia and the Bering strait, there are warming temps at 10 mb. You can see that above, as well as on the 0z Euro:

 

Above Iceland and N. Europe, but lower in the atmosphere, some dynamic cyclones are tossing some anticyclones toward the pole, and the bottom of the Stratospheric Polar Vortex (SPV):

You can see some anticyclones decaying over the pole in the early frames of the above gif, but I have also circled a more cohesive one. 

You can see it here at the bottom of the troposphere:

in both you can see the main areas of vorticity getting stretched out from Hudson Bay to Siberia and I think that corresponds to the stretched look the SPV has in the first gifs of this post. 

But beware, if you look at the 3D vortex, you can see that all this may just be something that is going on at the lower levels of the SPV (concave area over N. Europe):

 

Again not saying there is going to be a split, just decided to poke around in the strat. this AM. Doesn't always bear fruit, but something to watch. The anticyclones at the dynamic tropopause being tossed across the pole can be more meaningful, even if they don't disrupt the SPV, if they dislodge something or shake up smaller vorticies as they wander around the pole and towards Siberia. But that would have a 2 - 3 week lag for us and that is only if the GFS's depiction of anything late in its run proves accurate. 

Maybe Sandy Claws will bring us a present though:

 

[Carvers Gap]

To echo what John said above, the 0z EPS d10+ was a significant improvement, and an example of how we stay in a colder pattern with the AK vortex.  The tricky party of that is a -NAO/-AO couplet, and it has been some time since we have seen that feature stay for long periods of time during winter.  Might this be that winter?  I don't know.  That said, the 0z EPS has a decently consistent negative AO/NAO couplet.  This creates a feature which has been unusual during the past decade.  That feature is BN heights in both AK and the Southeast US.  That can happen, but help from the Atlantic is usually how that occurs.  One final comment...as I went to pull these up, it appears the big change is the AO over the past few runs of the EPS is actually more negative.  

[iluvsnow]

My hats off to you TV guys. I'm a long time, occasional participant in my home forum (OV/Great Lakes). When I want real analysis on long term model runs, you can't beat what you post. Sadly the guys in my forum seldom give analysis...but rather obs and complaints. Hey I complain too. We've all had a lot to complain about the last few winters. The Mid-Atlantic group does a decent job...but I go there more for the in-fighting and humor than meteorology. So keep up the great work. It is appreciated by me and many other out of region enthusiasts. 

[Daniel Boone]

7 hours ago, John1122 said:

EPS was night and day different 12z to 00z.  It went from a deep Alaska vortex at D 14 to a PNA ridge, -NAO look and a deep Eastern trough. 

Exactly the option we discussed that would get it done John. More than likely will be wavering back and forth between the two alot.  Saw where CPC Totally bought yesterday's solutions. Not surprising though, as percentage odds and recent climate persistence trends would dictate that from them.

[Daniel Boone]

1 hour ago, Carvers Gap said:

To echo what John said above, the 0z EPS d10+ was a significant improvement, and an example of how we stay in a colder pattern with the AK vortex.  The tricky party of that is a -NAO/-AO couplet, and it has been some time since we have seen that feature stay for long periods of time during winter.  Might this be that winter?  I don't know.  That said, the 0z EPS has a decently consistent negative AO/NAO couplet.  This creates a feature which has been unusual during the past decade.  That feature is BN heights in both AK and the Southeast US.  That can happen, but help from the Atlantic is usually how that occurs.  One final comment...as I went to pull these up, it appears the big change is the AO over the past few runs of the EPS is actually more negative.  

Right along you John and my thoughts  yesterday of the "how" to get a favorable pattern even with the AK Vort.

[Holston_River_Rambler]

In a wild plot twist, the RGEM, mentioned in my post above above as missing the phase for the first two pieces of energy, has now reversed that position and phases them more like the Euro did in its gif above:

RGEM thinks it could get interesting for SW VA and maybe, just maybe, TRI. All happening overnight Sunday into Monday, so that would help. 

 

 

The OP GFS and NAM aren't having any of it. 

 

Several of teh 18z GEFS members are similar to theRGEM though:

 

OP Euro now looks like what the RGEM looked like a couple of days ago:

EPS members aren't having any of it either. 

 

 

[John1122]

The EPS basically kept us BN again at 12z in the extended range due to a West coast ridge that holds the SE ridge at bay. By late run Alaska and the SE are the only BN areas around North America.

[weathertree4u]

12 hours ago, John1122 said:

The EPS basically kept us BN again at 12z in the extended range due to a West coast ridge that holds the SE ridge at bay. By late run Alaska and the SE are the only BN areas around North America.

Is this another Winter season where the cold and snow chances are always in the long range? Not really seeing it. Likely, hopefully, just because not aware of what or where to look. 

[Holston_River_Rambler]

Looking a little rough on the overnight EPS in the long range:

 

 

 

At least it looks like a drier mildness and more zonal pattern than we have had in the past couple of winters.  Might mitigate severe (sorry for severe lovers, not hating on you, just not a fan myself at least here where it seems like it is usually overnight and hard to see) and what has been our monsoon season for the past couple of winters. 

[Holston_River_Rambler]

NAM 3km (and the RAP, sort of) has an interesting feature for tomorrow AM moving off of the plateau into the central eastern valley and on towards the Smokies:

Looks like it has something to do with the 500 mb energy. Not that it would be a big event either way, but I will be watching to see if something like that happens. 

The NAM shows some frontogenetic forcing to the lee of the Apps, just as the blob of precip I circled would be moving over taht area:

so maybe there is something like that to the lee of the plateau as the 500 mb flow backs up the valley at the same time as some lower level lee side convergence happens just ENE of the frozen head mts? 

500 mb flow in blue,

700 mb flow in black,

850 mb flow in red 

The NAM sounding shows the best forcing and moisture just below the Dendritic Growth Layer, but some moisture up to 500 mb. 

Again this is not going to be a huge deal, but it is the kind of micro climate stuff I'm interested in. 

 

[PowellVolz]

Is this another Winter season where the cold and snow chances are always in the long range? Not really seeing it. Likely, hopefully, just because not aware of what or where to look. 

Cold and snow is like Covid. Always 2 weeks away.


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[Carvers Gap]

Sneaky system for NE TN and SW VA tomorrow.  Looks like light rain in the valley, but if this comes in over night with a period of clearing right before onset....

[John1122]

The next 10-14 days look volatile, at least on the Euro. Cold/warm/cold/warm roller coaster weather. The Euro loads Alaska with cold and occasionally ridging out west bumps a piece towards us. As for snow, all about timing but we will likely have a least one cutter in the next 10 days.

[Daniel Boone]

1 hour ago, Carvers Gap said:

Sneaky system for NE TN and SW VA tomorrow.  Looks like light rain in the valley, but if this comes in over night with a period of clearing right before onset....

Think that's the biggest concern for the lower elevations.  The longer the clear skies 2night the better.  Problem is, it's already beginning to cloud up. Worst case scenario; cloud up during afternoon as that seals in the daytime heat build up , then remain cloudy up to precip onset.  Don't you just hate that if you're a snow lover.?!

[Carvers Gap]

2 hours ago, John1122 said:

The next 10-14 days look volatile, at least on the Euro. Cold/warm/cold/warm roller coaster weather. The Euro loads Alaska with cold and occasionally ridging out west bumps a piece towards us. As for snow, all about timing but we will likely have a least one cutter in the next 10 days.

Beast of a -NAO showing up on the 12z EPS.  No idea if that verifies, but seems to be a feature that has some staying power(and not just in the LR).  What do you think?

[Carvers Gap]

The EPS ensembles are running about -1 for the NAO which is much more negative than the Weeklies from TR.  Will try to post some LR pics.  The EPS, if right, would provide us with some chances.  I don't think anyone has been promising a big winter, but that look is not as bad as I thought it would be.

[Carvers Gap]

The 12z EPS AO is at -2 in places.  So, looks like if we are going to have winter...the Atlantic is the ticket(think Jeff said as much in the winter thread).  The MJO continues to look putrid which is a surprise to me.  Would not be surprised to see it rotate over to 7, 8, 1 in a couple of weeks as some of the OLR maps show a diminishing wave over the warmer phase areas in the wester PAC and Indonesia. 

[PowellVolz]

WWA for areas above 2500’ in the smokies


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