Carvers Gap

Anytime, the SOI jumps like that...usually a big shake-up ensues downstream. Also is true in reverse. Things start moving. We don't want the SOI in strong El Nino territory. Santa brining the goods(meaning the gifs). Thank you!!!!

All three 12z global operationals reverse the current pattern over the lower 48 in one form or another...and especially off SW Alaska. The Aleutian ridge is currently digging a downstream western trough which is forcing a SE ridge. The weaker that Aleutian ridge after Jan 1, the weaker that SER and the more the cold pushes. Everything hinges on that ridge being displaced, removed, or weakening. The bigger development is seeing the GFS pop a +PNA. Euro has something similar at 240 with ridging building out West. Canadian just puts all of NA in the icebox.

Looks like the Aleutian ridge weakens more on the 12z EPS. Great thing is I think the EPS is getting into the part of the season where it is a bit more trustworthy - maybe. LOL. Operationals are very cold. Trends are good right now in regards to the Aleutian ridge. The GFS has been leading its ensemble for a few days....and it is a total pattern flip. For now, looks like a decent window for winter wx between the 3rd and 10th. Could definitely change as that is still a ways out there....key is the weakening of the Aleutian ridge. That SOI bump may do the trick. Do you have the gifs for the 12z operationals handy?

One potential we may see Went and looked it up. Below -8 is El Nino. Above +8 is La Nina according to BOMM. So, basically we have been in an El Nino SOI state( @John1122all over that) and now we are returning to a Nina(edit) state. That jump is going to create a shift downstream. Just looking at ensembles. Looks like the trough just goes nuts over the East for about 7 days beginning on the 3rd. Looks like that is decent window for storms if the STJ will stay as active as it looks. Then, potentially the trough lifts out....not convinced that is actually what happens but it could.

The 12z EPS is now very close to being in that CMC camp from a few days ago. Good trends. ALWAYS wary of the rug being pulled out...but seeing BN temps at the time when it is climatologically coldest is cold indeed.

The 0z Euro control, which has kind of been leading the ensemble for the past few days, is quite cold after the 3rd. "Bitterly" might be too strong of a word....but it is headed there.

The 12z EPS is much cooler through 300 than it was at 0z, and 0z was not too shabby.

That is Nino level, right? Like strong Nino? Would also be indicative of a pattern flip over NA pending I think. That is craziness. What is your take on that, Jax?

12z CMC is better in terms of the pattern here. Snow on the 3rd and then a cold period follows.

12z GFS with a complete pattern reversal again in the LR. The erosion of the Aleutian high begins around Jan 1 and is eventually replaced by a trough. PNA ridge replaces the strongly negative PNA. Likely the GFS is jumping the gun, but a fun run from a 500 pattern perspective.

Couple of general and finer points this morning in no particular order: 1. The Aleutian high is weaker, displaced from its current location, or completely gone in the LR depending on your model of choice. 2. The EPS teleconnection for the PNA goes from extremely negative to nearly neutral - positive on the control. 2. Pattern itself may become one dominated by -AO. Maybe the -NAO for at time as well. EPO showing some signs of cooperation. 3. Tough right now to say whether we are looking at a pattern reversal, a temporary relaxation, or simply 4-5 days of cold. If we hold to patterns lasting 4-6 weeks as a general rule, the current pattern is due to change during the first two weeks of Jan. That doesn't mean the new pattern is any better. I think it is possible on modeling that we are seeing the beginnings of that shake-up. Just tough to know where all of the pieces end up once the current pattern begins to erode. 4. The first cold front to set this in motion may well be Dec 31st. It is not overly powerful, but could potentially knock down the much above normal temps behind it. The Jan 3rd front could be fairly strong, but that is not a given. 5. Lots of things in motion this AM. Truly those have been seen on modeling for about a week, but we can "see" those changes now on operational modeling. Word of caution is that the base pattern seems to really be a trough in the Mountain West. However, the cold temps being modeled at times is just insane. There is a mid-1060s hp at the end of the 6z GFS run over MT and the front range of southwest Canada. That will change, but it shows the extremes on modeling right now. So, lots of stuff to get worked out. 6. Big takeaway is that extremes are on the map. If the Aleutian high weakens which in turn will weaken the monster -PNA...the cold has a legit chance of coming eastward - likely in waves with very warm temps between waves of very cold air. ALL OF THAT IS SPECULATION RIGHT NOW IN TERMS OF THE LR PATTERN. 7. addendum: The MJO is just crawling across 7...it is in no hurry. Several of the maps look a lot like 8. But work remember what John noted about low amplitude 7 a few pages ago...that is a cold signal for Atlanta.

Good morning and Merry Christmas!!! Fingers crossed, ensembles and operationals (speaking in general terms) are continuing the trends from yesterday. Let's see if those trends continue at 12z.

Hate to gum up the thread with a million posts about LR modeling...but the Canadian is about to go bonkers in terms of cold. Will simply post my comments here int this post so as not to add 10 more posts. If the 0z GFS had not feed back into that trough, this is likely what would have happened. No idea which one is right, but that looks an awful lot like what happened last February. Wow. Likely too cold, but the CMC has single digits over northern portions of the forum area with no snow on the ground which is impressive. We have seen these types of looks before....Head fake? Plausible scenario. Extreme swings? Also a plausible scenario. We have seen both head fakes and wx extremes during the past two winters. If the elimination of the Aleutians high is legit, we could see a November-esque pattern develop but I am way ahead of myself with that.

Indeed post 300, the GFS again simply gets rid of the Aleutian ridge. The gradient between Kansas and northern Montana would something like 80F to sub zero - very sharp. Trough likely goes into the east again as it did at 18z, but just a bit later. Just one run and likely will be different at 6z. It is now officially Christmas!!! Merry Christmas to the best wx forum in America. Hope everyone has a great day. I will try to post some, but tomorrow will be busy. Keep the home fires lit.

When I talk about pay me now or pay me later with that big ridge hooking into the NAO....If memory serves me correctly, the reaction during past years has been quite abrupt regarding the TPV - not the usual waiting game for an SSW to propagate downward. Now, I am not sure this run is even realistic given the aforementioned feedback, but in the off chance this is even closely correct....cold air would likely be jettisoned towards the mid latitudes quite quickly.

Oddly, the problem this run is that the NAO is so strong(big change since 18z and maybe not a great change) is that the NAO just bottles up the flow. I think it still gets to where 18z did but a day or two later. The mid continental ridge feeds into the NAO in a pay me now or pay me later pattern regarding cold. That big ridge is a tell tale sign of an SSW that would almost certainly disrupt the TPV and SPV.

Though the 0z GFS is a much different variation, after 300 it is beginning to weaken(or eliminate?) the Aleutians ridge again. If that trough doesn't free back off the coast of California, it would flip the pattern again...may still yet do it. We'll see.

Looks like there is problematic feedback within the model with the storm that drops southwest out of split trough(?). It should recurve toward the coast a bit more quickly which delays the downstream response over the eastern US.

One recommendation...With so much cold, it is wise to actually look at surface pressure departures and surface anomalies. What looks like a warm map at 500mb can actually be quite cold at the surface sometimes. 500mb is roughly 16,000-20,000' above sea level. Definitely truly on the 0z GFS.

Merry Christmas to everyone!!! Though warm, it is a beautiful night here in NE TN. Watching the 12z GFS roll-in. Yet another variation of the Jan 3rd event. Cutter and this unleashes very cold air between the Rockies and the Apps.

The 18z GFS again flips the pattern...just switch the blues and reds on Tropical Tidbits over the US in the LR. Basically, the Jan 3 cold front begins the flip w a transient ridge after that cold front. No idea if that verifies, but impressive nonetheless. If a pattern change does a occur, the CMC and CFSv2 score the coup.

Grabbed this from the MA forum...great write-up about the potential seen today in modeling by @brooklynwx99

General trend across the board today(operational and ensembles) is to weaken, severely displace, or completely remove the Aleutian high. Opens the door for cold if true. A true MJO 7 would allow for that. As John noted, the atmosphere has been more a 6. Generally speaking, seeing a large area of BN temps slide eastward and expand between the Rockies and the Apps. In between Christmas activities, so hopefully this post hasn’t missed something major! LOL

12z EPS is a fantastic run and ensemble at that. @jaxjagman, hang in there. Glad it is getting better. Great to see you on the forum more.

Guessing the GFS is jumping the gun, but the continued erosion of the Aleutian high is apparent on that model yet again.