Carvers Gap

The Euro Weeklies are full bore winter in January. They have increasingly BN temps. That LR ext ensemble and the GEPS have broken towards cold today. We were waiting for ensembles to track....some good trends. In the case of the Euro Weeklies...great trends. 95-96(lite) and some 84-85 vibes as you all noted earlier in the thread.

The real fun with that is the NAO and Aleutian's highs bridge across the top. They trap a lobe of the TPV in NA. I think the biggest take away from 12z is that HL blocking is showing up across modeling, and the signal is stronger at 12z than yesterday at this time. Good trends.

Models have "likely" made two big errors this year. One was the Baja low situation for early December. The next one(appears as of now) was the repetitive lows sliding out of British Columbia to off the Coast of California. The Rex block might produce one or two storms on the West Coast...but not the sequence which was causing the endless chinooks. Even though modeling is still working things out....the exiting of feedback helps. Some chinook makes sense...but it was way overdone it appears. Now, is the NAO feedback? IDK. I have definitely witnessed years when models over-did how strong it was and missed the duration (sometimes too little duration...sometimes too much). The same could be said for the Aleutians high - but it has actual precedence for being there and at that intensity. I think we end up w/ a full latitude trough w/ cold dropping into Montana, modifying just a bit, and then heading eastward. I think the difference this year(compared to recent Nina winters), the source is much colder and this cold finds its way all the way to the Atlantic coast. I do suspect models could be too quick with the move back to cold, but again, sometimes they aren't quick enough if the NAO is going to be a player. The storm track could be more favorable as we enter January. As your friend notes, mid-Jan makes a bit more sense or even just the second week of January.

12z is definitely a choose your own adventure. Definitely NOT an easy pattern to model, but LIKELY to produce some interesting solutions on deterministic runs. Normally, I would say check the ensembles, but I think they are at least 24-36 hours behind the curve.

Haha. I am a time traveller.

I mean...really these are some WILD solutions. The 12z Euro is cooking one up as I type - doubtful it verifies. Good trends, but wild.

Even the Euro AIFS at 12z(which has been reluctant of late to budge) completely erases the chinook pattern. I think some version of a full latitude trough w/ some ridges/troughs sliding across the base...sure makes a lot of sense.

Between 180 and 240, the CMC completely erases any remnant of the chinook, and fills NA w/ BN temps again. Impressive if it is real.

12z CMC is on board and about 2-3 days quicker as it has been for a bit. The mechanics for cold an snow are in place around the new year if these trends hold

I suspect the 12z GFS is just a bit quick, but that is a potent winter weather pattern just after 300 that run. By the end of the run, the blues and reds are in the right places w/ split flow. That is a plausible(though certainly not certain) solution. Great trend if it sticks.

If the CFSv2 seasonal is right this morning, LC is could be set to score a pretty coveted seasonal win....and I mean an outright thumping. He dared to go the exact opposite of many seasonal ideas.

Ideally we want the cutter. I think it shakes up the 500 pattern. As for wind, hole mackerel it is howling out there. On my run this morning, I saw a roof blown off shed, and poly from another roof. Constant roar out there right now.

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.