Carvers Gap

With opposing teleconnections (high in the Aleutians and high over Greenland), modeling "could" have its hand full. The base pattern would be an eastwardly displaced PNA ridge w/ cold attempting to stretch from Alaska into the NE. Cold would roll over the top of that ridge and any storm(Miller B or A) would bring down very intense cold behind it into the SE. I wouldn't say it is a great pattern for snow unless we can score an inland runner. But...it could get crazy cold IF the NAO is as strong as projected on both the Euro and CMC(especially the GDPS). FWIW, ensembles aren't seeing cold fronts at all - just completely washed out until the last minute. That is why I am using them less. It is entirely possible the NAO does not develop, but it is infamously difficult to predict. I am a bit wary of any model where it is absent late in the run. The wind is absolutely howling here....that must be what you all were describing.

The first thing we are gonna have to know(and it is increasing in likelihood) is whether the NAO is a legit player. On modeling where it is missing or weak....it is warm here. When it is present, cold fronts drop through the Plains(instead of sliding through Canada).

The para 0z GDPS is very cold on the 28th-29th before the run ends. I have a feeling (if the NAO strengthens and models aren't hurrying it up too much), that cutter may bring down more cold than models are depicting. If the NAO starts a bit slow, then the GFS will score that timeframe.

Line moved through here this morning. Wind and rain. Both the 0z CMC and Euro move plenty of cold air eastward beginning around the 29th. They could be too fast in breaking down the warm-up, but both have a cutter where the GFS does not. My guess would be the GFS is slightly too progressive, and misses it. If that cutter is legit, cold would roar down the Plains. Not sure how excited about cold on the 30th I am - Music City Bowl would be miserable!

Haha. I was teaching 3rd grad that year. We ran out of snow days in Knox Co...like ran waaaay out of snow days.

The one thing that makes the Weeklies(any brand) fallible is that they tend to perpetuate the week two pattern - true feedback. That is why it is important not to put to much stock in LR ext modeling unless IMHO they change from that two week pattern. In other words, if the model doesn't continue in perpetuity...that is worth paying attention to. I have seen cold patterns modeled for all six weeks...not even make it into week 3. That also works for warm air masses. So, that is why I like looking at the control which is basically just one big deterministic run.

Cherry picking some stuff from the Euro Weeklies, though I didn't think the ensemble was half bad!

@nrgjeff, are the new AI ensembles decent? I notice the 12z GEPS and both AI ensembles (GFS/Euro) had a lot of cold members after 300. The Vols losing three straight was like looking at non-stop chinooks on modeling - same result, same set-up. We needed that Louisville shake-up(red like an NAO! - it's a sign).

I like it a lot better than 16 straight days of chinooks on deterministic runs. LOL. It might still get warm, but I gotta have room for some surprises.

The 12z Euro takes the GDPS/CMC route, and quickly establishes influence by the NAO, but it quickly loses it. I think modeling at 12z is on the struggle bus(not abnormal) w/ the NAO. I have seen the NAO absolutely wreck what looked like very nice, consistent patterns. It is a bull in a China shop. There is a lot to like about this still frame. There is a lot to not like about what happens next! Haha. But we take this over a chinook any day of the week. By the end of the run, the Euro looked to resolidify the NAO and swing the big trough east. Almost all modeling is teasing sending that western trough eastward. It "could" be too quick, but some the CMC and Euro are about 3-7 days quicker depending on the run. IF the NAO block is legit, it is going to create more wild solutions like it did at 12z. If we can get any help from the Pac....then bigger things are on the table. spell check will be the death of me....

Unfortunately, the Aleutian Ridge has been a staple of recent past Nina winters - the big red ball on 500 maps. If forces a Rex block. Models have a very difficult time "knowing" when it ends - much like the NAO. I don't think there is a lot of data in that area, and that can be a problem. It seems like the Aleutian Ridge has a tendency to disappear with little notice, and the trough kicks almost immediately eastward. Those ice and snow storms that middle and west Tenn have experienced occurred when that Aleutians Ridge pattern relaxed. It seems to me that usually occurs between the first and third weeks of January. I know some think the trough retrogrades and does not come back. If the NAO goes negative, that could balance things out. We lacked the NAO w/ recent analogs where the trough pulled back, and wouldn't budge. There is a lot of uncertainty going forward. I generally like uncertainty, because that leaves room for crazy weather. In winter, that could be anything from severe (which I don't like) to winter storms. I think the key going forward is the NAO going negative. It is the ingredient in many EC storms. That doesn't necessarily help you all just to the west...but it can force sliders in addition to coastals.

The 12z GFS has pretty massive feedback issues. I don't really have a problem w/ a trough off the West Coast - that happens. The 5-7 days of endless vortices spinning up just doesn't make sense. Just when I thought it had that worked out....it is right back to it. The 12z GFS really doesn't have a -NAO either. We need the NAO to establish HL blocking and force the issue I think. The GFS is just way off on its own by 300.

The reason I posted these is to illustrate that sooner or later the NAO is gonna put the squeeze on this pattern. The NAO is a trump card as is the EPO. If one is in play, that is a good thing regardless of the MJO phase, etc. The tendency is for the trough to find its way eastward when the NAO is present on modeling. The 12z GFS shows what happens when it is late to the party. The Canadian suite is most definitely the fastest flip.

The 0z GDPS probably had the best looks by 240. Trough in the East, split flow, -NAO...I wasn't gonna post it but might as well. To me this makes sense IF the NAO is legit. The 12z GFS is out in the weeds....

This is only ten days out...this isn't the Weeklies or 300+. That sure looked like it was going to slide the trough from the GOA right into the nation's mid-section. That ridge over the eastern Pac wasn't moving.

And, eh, not terrible...ridging in the Eastern Pac. I thought it might go to crap after this, but the NAO took a shot of the juice and the EPO fired.

I just wanted to introduce my new friend...

@nrgjeffif you are gonna give us some wx goods today, we must talk basketball. After a three game skid, the Vols finally showed some promise with that win over Louisville(though admittedly missing a key guard for that game).

There will likely be some model chaos(and even real time chaos) w/ two strong and very opposite teleconnections IF they verify. The Aleutians Ridge and -NAO are not going to play well together. I suspect we end up w/ a very similar pattern to what we exited, but maybe with the pattern being forced south of where it was due to the NAO and seasonal climatology. It seems like the Yukon will be cold and will send cold air southeast into a suppressed storm track. I do think ridges will roll through between cold shots. But we roll the dice and take our chances if that is indeed the setup. Suppressed storm tracks with cold involved...we take. The nice thing is that most of the models are eliminating feedback over the Pacific Northwest, and we can see what is a reasonable pattern unfolding. Infinite Baja lows and Pac NW lows.... I guess the question I have now is if there is feedback w/ the Aleutians low and maybe the NAO? Those are two other areas where models will sometimes under-do and over-do things.

The -NAO is the story if it unfold the way modeling has shown it for the past 48 hours. I don't think it will mean a trough 100% of the time over the EC, but it "could" force the storm track well south as we have see on overnight runs. The 0z Euro and now 6z GFS.....what a turn of events.

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The 18z GFS appears to have lost most of its feedback with BN heights coming over the pole at to crash into the eastern ridge. The NAO bout to be tested this run. Let’s see where it goes. Just looking for consistent trends at this point and not random solutions. -only minor feedback on the West Coast this run. So far... -at 300, that is a big time trough in bound...and a monster NAO -Shortly after...the chinook pattern is gone. - Basically, the Chinook has from Dec 24-29th to do its work. It might be the most overtracked feature across forums in many years. Turns out, this may well just be your standard warm-up after a cold spell. -the mechanism is n place late in the run for a full latitude trough w/ trough wedged between an west Alaskan block and a Greenland block. -trough dives west at the end of the run, but almost certainly would have to kick east. There is a little bit of feedback along the WC again. If the trough dives through the front range and not along the coast....that would bring bitterly cold air into most of the country. -right now we can see modeling correcting away from feedback. How do we know that? Infinite vortices are not forming off the coast of Washington State. -Important...what makes more sense it that a double block(omega) is forming(a bit non-traditional) in the medium and long range. Energy is diving down the left side of the trough, gets kicked eastward, and the right side of the block slows down the energy and forces it north. The Rex block has trouble forming(thorn in the medium range) as the NAO exerts force. What I expect to happen is the NAO(if it is real) eventually forces an EPO or PNA to pop...ridge comes East. That almost fits what I "think" will be the MJO rotation with a more sustainable eastern trough by roughly mid Jan give or take a week. The NAO could speed up that transition...so it has to be watched.

GaWx has a nice run-to-run post about the 12z GEFS and how it started to lower heights over the NE in response to the NAO. I have had the NAO wreck my ideas more than once(good and bad) both when it appeared suddenly or didn't appear as forecast. It is a true wrecking ball. Until models sort it out, proceeding with caution is wise. I agree.

The GFS and the GEM (if one extrapolates past 240) continue to tease some big changes just after d10. The NAO is trying to be a player. It backs up the entire flow upstream and basically resets the 500 chinook pattern. Is it right? IDK. If we can get a storm to hit the West Coast near Los Angeles, that might do the trick in flipping the trough back East.

12z suite is rolling. I am going to put my thoughts on this suite in this single post. I will simply update it by editing. Feel free to comment. Just know this post is going to have several comments. So, you might "like" one thing, and it might be followed by something you don't like. Haha. 12z GFS -The GFS is really the first model to correct the Pacific NW. It has beens slowly doing this very several runs. Let's see where this run goes. I generally just toss the run if a slp wonders from British Columbia to 500 east of LA. 6z had a realistic solution. -@ 132 the GFS is flirting w/ a winter event over SE KY, SW VA, and NE TN. Probably is WAA, but tough to tell. Interesting development which I don't think has been there before. -The interesting thing is that there is a hp sitting over the top of that. -@ 195 that looks like more feedback over the Pac NW. Interestingly, there is an EPO ridge forming(temporary?). Definitely seems like this timeframe is a demarcation between a good path back to winter weather and on that is not. -@204 that storm off the coast of Cali looks like it might move inland. Any storm that enters at the latitude of Los Angels has to be watched on the EC. Many times a storm will enter and exit at similar latitudes of NA...not matter how far north our south they wonder while over the continent. -@240 generally I just look at the long wave pattern as details are going to change by the next run. The GFS got lost around 195...and ended up with a much different solution -the Dec 22nd cold front is present w/ wintry precip on its northern edge as it departs...big take away and we'll see if it sticks. -I should add that the -NAO is present on this run, but slightly less strong. The NAO is very difficult for models at range, but can make big difference upstream if they form a block. -As wild as that run got, it pretty much got to the same point that 6z did by 270. -300+ The GFS puts the trough back in the East(temporary?). The run-to-run change graphics for this time frame are gonna be fun - really fun. -On both the GEM and GFS...the NAO is east based but having a major effect on the 500 upstream pattern of all of North America. Right now, the GFS has a window from Dec 23-Dec30 for the chinook. Then, recent deterministic runs tend to slam the door on that by the New Year. The real fun begins is if the 6z GFS run blends w/ the 12z run at some point....chinook muted and then trough into the East. Don't know if that can happen, but w/ the MJO in the COD, the SSW may be taking the driver's seat. The NAO would likely be a result of that. 12z AIFS -Looks remarkably similar to the GFS. Looks like around 300 it wants to send a decently amplified trough eastward. Not sure if that is temporary or not, but w/ the NAO sitting up top...that teleconnects to an eastern trough more times than not with the usual caveats mentioned by Boone and me in early posts.