December 2020 Medium/Long Term Pattern Discussion.

[Daniel Boone]

Noticed Dierks on WCYB this evening mentioned just a low chance of a turn over at the end for end of week system and showed a model run. He is a good Met and guy but, is warm biased.

[PowellVolz]

RGEM out to hour 84 verbatim would be a heart breaker, but I suspect, if this were to verify, there might be more fun after hour 84:

 
 

You make great gifs. It really simplifies it for those who have less knowledge. Thanks


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[Holston_River_Rambler]

18z Euro is dancing to the NAM's tune.:

I don't have the precip. maps yet, but look at the energy racing in from Canada. Someone in the interior from PA to ME is gonna get blasted if this whole thing comes together. 

[Wurbus]

It is fantasy land, but what a beauty at the end of that GFS run. It has been hinting at something around mid-December. It is at least a window to watch. It is also followed by some bone chilling cold.

[John1122]

46 minutes ago, Wurbus said:

It is fantasy land, but what a beauty at the end of that GFS run. It has been hinting at something around mid-December. It is at least a window to watch. It is also followed by some bone chilling cold.

 

This comes about with a ridge on the West coast and the elusive -NAO working in combination. 

As long as we can keep the Pacific on board we have shots of getting cold and a suppressed storm track. 

[John1122]

If you like bone chilling cold, this is the map for you. EPO blocking in Alaska and NAO blocking creates a -AO as well and the takes the cold from Siberia and dumps it through Alaska and into the Lower 48, aimed perfectly at our region.  

[weathertree4u]

2 hours ago, John1122 said:

If you like bone chilling cold, this is the map for you. EPO blocking in Alaska and NAO blocking creates a -AO as well and the takes the cold from Siberia and dumps it through Alaska and into the Lower 48, aimed perfectly at our region.  

We are overdue for a true arctic outbreak imo and it would fit well with some of the analog years I have seen like 1989

[Holston_River_Rambler]

So much flipping and flopping by models on the weekend system. Now the 6z NAM has gone to almost totally losing it by dumping more energy over N. Mexico. But now, even though the Euro still has some version of it, both the NAM and the Euro seem to be seeing a chance for the left over energy to interact with another (lol) piece of N. stream energy.

As it stands on the 0z Euro it would be too positively tilted to do much for us, but as Carvers has noted there is soooo much energy flying around, it almost isn't worth looking at either this weekend's set up or the one I gifed above, more than 24 hours out, if that.  

 

Like Wurbus said, models really like the Dec 14 - 17 period for some sort of storm in the east. It fits one of the ways we get storms, as a pattern is shifting or reshuffling, or breaking down, a period ensembles are starting to see at the very ends of their runs. Storm-->arctic dump-->pattern shift.

EPS's vision for that window, as of 0z today:

 

But as the EPS city charts hint at, there are cutters, miller As, and Miller Bs all mixed in there and even some where a cutter leads to a Miller A/B. Tis the season for hope though, until it isn't, lol.

 

 

 

 

 

 

 

[Wurbus]

I'm not sure where to post this, but looks like the HRRR was updated.

[Carvers Gap]

Just looking at today's MJO forecasts...beware.  The MJO has gone weak sauce(even more so than the last mention of it I had) - meaning it can barely get out of the COD.  The ensemble clusters are either more COD or very weak 4-5-6.  The hi-res models, which at one point propagated into warmer phases, are literally stuck in one place.  I think this is likely why we are seeing the look that John noted last night which is a trough stretching from AK to the SE.  Normally, one would think the SE would have a ridge blunt that cold intrusion.  IF(emphasis on IF) the MJO is correct, it may be muted if today's ECMWF and NCEP modeling is accurate on the CPC site.  That might ever so slightly open the door for a colder SE than once thought after Christmas.  Just spitballing, it might mean we get a normal cold configuration of La Nina, but the SER might be muted enough that cold could head SE.  In recent years, that cold has had trouble getting past the Plains, but that was with a very strong MJO which seemed camped out at high amplitude in the warm phases of 4-6.  

[TellicoWx]

1 hour ago, Carvers Gap said:

Just looking at today's MJO forecasts...beware.  The MJO has gone weak sauce(even more so than the last mention of it I had) - meaning it can barely get out of the COD.  The ensemble clusters are either more COD or very weak 4-5-6.  The hi-res models, which at one point propagated into warmer phases, are literally stuck in one place.  I think this is likely why we are seeing the look that John noted last night which is a trough stretching from AK to the SE.  Normally, one would think the SE would have a ridge blunt that cold intrusion.  IF(emphasis on IF) the MJO is correct, it may be muted if today's ECMWF and NCEP modeling is accurate on the CPC site.  That might ever so slightly open the door for a colder SE than once thought after Christmas.  Just spitballing, it might mean we get a normal cold configuration of La Nina, but the SER might be muted enough that cold could head SE.  In recent years, that cold has had trouble getting past the Plains, but that was with a very strong MJO which seemed camped out at high amplitude in the warm phases of 4-6.  

There was a study done on one of the old forums several years ago centered around Atlanta regarding what phases/amplitudes they scored sig winter weather in...surprisingly the COD produced more than any other amplitude. I believe you hit the nail on the head...to score we have to rely on a weak version of the SER (more so for the eastern side of the state. Over amplify in cold phases and the cold overbears the Gulf...reverse for the warm phases..torch city.

[Holston_River_Rambler]

12z Euro closer to something interesting with the second piece of energy as it kicks out of the SW and interacts with a N. stream piece. 

Pieces are there on the GFS, CMC, UKMET, and ICON, just a question of how they all dance. 

[Fred Gossage]

MJO looks to be going toward a position a bit more typical of La Nina as we head forward, and AAM looks like it's going to start tanking soon.  I would start keeping an eye on medium range guidance for one or more severe weather threats to start showing up between now and Christmas or so.  No real specifics other than that, but it may be time to start having our eyes open...

[Carvers Gap]

12z GEFS and GEPS definitely showing a trough which slips back into Alaska after 300.  LR guidance has been bouncing around with how far that cold can intrude into the US.  Depending on where that boundary sets up (the AK trough potential nosing SE) will tell us a lot about things going forward after mid-month.  

As for severe, the "thunder in the mountains" saying (snow within 10-14 days) has been pretty sound in recent years....

If the MJO can make it out of the COD, will be interesting to see how long it stays in the warmer phases.  Some schools of though out there that it may just keep going which would be fine by me.   

After the system this weekend, there may be a few shots of cold/snow showers after that...we will see if that trough lifts out with the storm or digs in for a few more days.

[Carvers Gap]

The 12z EPS is not a bad look in terms of cold.  Probably will be some cutters involved with that look as well which definitely could produce some rumbles of thunder in NE TN.  One interesting thing I noticed is the ridge backing into the Bering Strait.  Normally, I am not a huge fan of that, but there are some winters where that was prominent and are notable exceptions to that thought.  January of 1996 is one of those analogs.  In the Northern Hemisphere, the January 96 analog looks nearly identical to what the EPS is depicting at the very end of its run.  Yesterday, I thought aloud about whether this winter would be like 89-90 where winter started early and evaporated or if it would be like 95-96 where it continued - obviously any 95-96 reference is a "lite" version as extremes like that are exactly that - extremes.  If I get time later I will share the similarities, but one of those similarities is a ridge off the end of the Aleutians and extending into eastern Russia.  Rainshadows 59-60 comparison is a good one as well.  No idea where this pattern is heading after Christmas, but just kicking the can around a bit.

[Daniel Boone]

1 hour ago, Fred Gossage said:

MJO looks to be going toward a position a bit more typical of La Nina as we head forward, and AAM looks like it's going to start tanking soon.  I would start keeping an eye on medium range guidance for one or more severe weather threats to start showing up between now and Christmas or so.  No real specifics other than that, but it may be time to start having our eyes open...

Same things were brought up back in '95-96 Fred as well as 2010-11 and a couple Factors warred against the full La Niña pattern takeover . Oh yes, it did try especially in 95-96 as short lived bouts of mild would come east only to be shunted by strong blocking in the NAO domain and other areas as Carver aluded to.

         Of course, Niña was weak that season so, odds are less favorable for that yo happen now and more in favor of more niña influence.  However, what about 2010-11 ? Strong Niña but, remained cold overall in the East. Blocking was one reason. What was the others ?

[Fred Gossage]

9 minutes ago, Daniel Boone said:

Same things were brought up back in '95-96 Fred as well as 2010-11 and a couple Factors warred against the full La Niña pattern takeover . Oh yes, it did try especially in 95-96 as short lived bouts of mild would come east only to be shunted by strong blocking in the NAO domain and other areas as Carver aluded to.

         Of course, Niña was weak that season so, odds are less favorable for that yo happen now and more in favor of more niña influence.  However, what about 2010-11 ? Strong Niña but, remained cold overall in the East. Blocking was one reason. What was the others ?

I'm very much not talking about the full winter.  I am simply saying that, for the next few weeks, we are heading toward a pattern that would possibly favor one or more severe weather threats between now and Christmas.  I honestly expect us to flip back and forth between the current pattern and the coming pattern for the rest of the winter.  CFS in particular wants to take the MJO back to the Pacific during some point in January and into February.  I kinda expect it to do that given what we have seen thus far.  February 2011, the MJO didn't budge from the Pacific.  My post had nothing to do with expectations for the winter overall.  It was telling folks in this area to start paying attention to systems ejecting out of the Plains between now and Christmas.

[Holston_River_Rambler]

Blunderstorm, Kentucky, and upper E TN folks, what the long range NAM taketh away one run, it returneth, yea yes and verily, on the next:

 

[Daniel Boone]

51 minutes ago, Fred Gossage said:

I'm very much not talking about the full winter.  I am simply saying that, for the next few weeks, we are heading toward a pattern that would possibly favor one or more severe weather threats between now and Christmas.  I honestly expect us to flip back and forth between the current pattern and the coming pattern for the rest of the winter.  CFS in particular wants to take the MJO back to the Pacific during some point in January and into February.  I kinda expect it to do that given what we have seen thus far.  February 2011, the MJO didn't budge from the Pacific.  My post had nothing to do with expectations for the winter overall.  It was telling folks in this area to start paying attention to systems ejecting out of the Plains between now and Christmas.

Gotcha ! Thanks for the clarification.  I expect back and forth as well. MJO does rule the roost many,( if not most, times ) tbh.  

[Holston_River_Rambler]

The overnight Euro and AM GFS still like something like a clipper with the next piece of energy (not the one for this weekend, but early next week). Snow looks elevation/ time of day dependent for now.  

 

 

 

The mesoscale models haven't gotten that far yet, so will be interesting to see what they do with it over the weekend. 

Ensembles have it too, but with a spread between nothing and more interaction with s. stream energy. 

Late bonus add UKMET:

 

[Holston_River_Rambler]

Here are the overnight ensembles for those interested. Not much change as far as I can tell:

 

 

Trough is wanting to shift N and W. 

 

Convection has has seemed to have picked up over the dreaded Maritime Continent (MC) over the past couple of days, after a nice flare up in the central- Western Pac, but this AM at least, it looks kinda anemic and scattered again, compared to how it looked when I checked last night. Also note the "Pac Jet of Woe"(c) screaming across the central Pac.

 

It may be that the lessening of convection this morning led to this solution on the OP 6z GFS:

what had been just a big ol cutter, now looks like a more easterly, weaker cutter, with a  little wave riding its front from the Gulf up the coast. 

To be fair there's probably more going on that a slight change in Tropical Convection. Correlation doesn't mean causation, but I have noticed sometimes or at least think I've noticed (lol) how the way models see that convection has impacts in their solutions. 

 

 

[Carvers Gap]

Looks like LR range trends overnight after say d12 are for the EPO/PNA to be positive.  The one silver lining is the AO and NAO couplet are negative.  Likely means that will the trough is in the West, there will be cold moving eastward periodically over time.  That said, let's see if all of that actually verifies.  Many of the LR models completely missed the cold during the first two weeks of December.   One thing I have noticed is high pressure really want to park itself right over the NW PAC warm pool.  So, there may be issues with a deep trough being able to establish itself in the West.  

[Carvers Gap]

I do think we will see one more eastern trough amplification prior to BN heights pulling into the Yukon after mid-month.  Also, the NAO/AO couplet is a huge wild card along with the PV getting disrupted.  I suspect that the weak MJO is going to allow for more mischief than last winter, but again, that is not an earth shattering prediction given how bad last winter was....I actually though the GEFS extended didn't look all of that bad last night(runs once per day).  

[Carvers Gap]

Just digging through the global ensembles this morning, I think I like the time frame between Dec10-17th in terms of more chances for snow.  I wouldn't rule out some snow showers early next week in NE TN, but a good rule of thumb for northern stream energy at range...often trends well north of original modeling.  Very well could see some cutters driver the cold boundary south and east of the area between now and the 10th. 

[Daniel Boone]

My thoughts are exactly with Carvers. That NE PAC warm pool along with HLB are fighting any Niña takeover . 

    IF Eps later depiction is right, it appears HLB may gradually force that vortex in the Yukon south. Probably down into south central Canada then who knows from there. Down into US or into eastern Canada.

[Carvers Gap]

12z GEFS really holding that ridge in the West(though suppressed after d10) along with BN heights in Alaska.  Very warm temps in the western states as a chinook is cranking.  Looks like a combo of Pacific and Canadian air for here as some of that Alaskan cold makes its way SE towards the EC.   Persistent AN temps in the West to even much AN.  The MJO still is a fairly weak signal.  Some modeling does have clusters that try to rotate it back into the COD or cold phases after a quick trip at low amplitude into the warm phases(measured in just a few days).  The SE still remains fairly chilly to seasonal.  Going to need more cold air for a winter storm pattern, but not as warm as 6z.  I would say this is a timeframe(d12+) of high uncertainty.  

[Carvers Gap]

12z GEPS(Canadian) starting the d10+ time frame with a much deeper trough in the East.  Ridge out west is proving to be a stubborn feature.  Will update in this post for the rest of its run if I get a chance.

...Not going to post much more as the run at 258 is much colder(just looking at 500) with another shot of cold air coming from upstream.  It may well eventually revert to its 0z look, but that is a rally cold look.  

[Carvers Gap]

For those new to the forum, this is what a lot of us look at(maybe not this company, but overlays or side-by-sides) of previous runs in order to see trends.  This is the 12z(left) and 0z(right) of the GEPS(Canadian ensemble).  You can see the trough digging much deeper with the EPO really stout.  Now, it likely still lifts out...but that is a pretty significant change.   This is at range and changes are to be expected.  IF it were to verify, that is a very cold look. The difference at 500 is Ohio to central FL in comparison between runs at 500.

[Holston_River_Rambler]

EPS looks pretty similar at that timestamp:

 

[Holston_River_Rambler]

Interesting beyond the gif above. It seems like that western ridge is reluctant, as you were saying, and the TPV is only pushed over by a building Greenland block, if we take this verbatim. Will be interesting to see how it plays out and how it looks without the smoothed mean. Some of the images were missing on weathermodels, so that is why it blanks out a bit towards the end.