Carvers Gap

So, basically the split is shown on the 18z GFS around 10-12 days out. Usually takes a couple of weeks after that IF it is going to send cold southward in the troposphere. Timing on that would be the first or second week of December if North America benefits at all.

Yeah, not sure I want to see a SSW and subsequent SPV/TPV split that early. Now, if one wanted a wall-to-wall cold winter...those can start that way. I don't see that happening BTW. OTH, we could see our early cold December dump westward (climo says eastward in December), and we could see DJF go warm. Man, I am kicking myself for not seeing that. The massive warm-up along the East Coast is often a pre-cursor to big SPV splits. Mega kudos to Jax for point that out. Hope you are doing well, man.

Ha! Ha! Man, you have a to tell me when you know a split is coming. I had heard rumors and just looked at the 18z GFS due to your comments. Textbook split.

Yeah. SPVs tend to favor EurAsia. When we do get the split (and equatorial push of Arctic air) in NA, it favors the west. We have had some really good winters with the SPV and some really craptastic winters. The year with the Memphis sub-zero, multi-day snow storm...that was a good SPV split if I remember correctly. Seems like we do well with maybe 1/4 to 1/3 of splits. If we want winter to continue into Jan/Feb this year, we may need one. The positive QBO lends itself to less blocking. Nina should help early on, and hurt us later on....Right now, looks to me like we are setting up for a mid-Nov to late Dec cold shot, and then we could be done with the exception of thread-the-needle stuff. That early season cold pattern(potential...not certain) should not be related to the SPV, though admittedly I haven't looked at stratospheric stuff much at all in about 2 weeks. That thing could be on fire right now, and I wouldn't know. LOL. Then, Nina climatology should send the trough into the Mountain West during Jan/Feb - where it is now actually. So, if the SPV trough normally goes there anyway and Nina has it in the Mountain West anyway, I am for taking a 1 in 4 shot in splitting it and sending it eastward mid to late winter. Again, I think the rising QBO really argues against blocking after December. QBO should flip back to a more favorable cycle next August or so. But some winters don't behave. A third year La Nina is a total crapshoot in the meager analog packages available for that rare occurrence. You guys have had some great recent winters in middle TN. Knoxville has done OK as well. The closer one is to the Apps, the less these past Nina winters have been helpful re: snow. I think you all get one more potentially good winter before the ENSO pattern switches up to one which favors coastal tracks next winter as Nino takes hold.

If ever there was going to be an outlier(Grid references those), it is this year. Why? Climatology has been wonky for the past 4-5 years - almost doing the exact opposite of analogs at times. I believe this has to do with the temperature gradient in the Pacific being for uniform that stratified during ENSO events(reference one of the guys in New England for that...TyphoonTIp I believe). I do think the mean trough will be centered in the western Plains and Mountain West w/ intrusions into the East. This warm November is gonna flip hard to BN temps I believe. If it does that, I think the La Nina pattern is likely going to be a traditional sequence of BN/Seasonal December -> early cold shot January -> WARM February and and early end to winter. 2023-2024 I am about as bullish as one can be. -QBO, weak El Nino after 3 La Ninas, Pacific SST gradient reset after this cold episode(should accentuate the El Nino response here)....loaded for bear.

Legit snow set-up for next Thursday(16th to clarify) if the GFS at 12z today is to be believed. That window has shown up on multiple runs. Still, the GFS has shown those only to be in error - so huge grain of salt.

Euro during shoulder season is less than accurate for sure. It seems to lack the ability to see cold shots. However, the model is still usable when it does that. Just have to see only when he warmth backs-off, and usually that is when BN temps move through. Its seasonal is very warm for winter. Even though it is biased warm and it is shoulder season, its solution is plausible. We actually have not had a "stinker" of a winter in some time west of the Apps. Generally, we have had a storm or two that drops some white stuff(Chattanooga excluded). There are, however, winters in TN where it snows very, very little at all lower elevations. We are long overdue for one of those. That said, I think we see some extreme cold at some point west of the Apps. Base-warm winter pattern though looks to be likely - QBO, solar, IO, and Pac are bearish for sustained cold after December. But who knows? Recent climo patterns don't really follow the rules the mid-late 20th century. Winter has already set-in out West and is right on time. This also fits Nina climatology. IMHO, December is our best shot, maybe early January.

The GFS and CMC are MUCH colder for next Saturday, and have a crazy hybrid system embedded. Let's see if that flip to cold holds at 12z. Major changes overnight on those two models. Euro isn't buying it quite yet.

Strong cold signal showing up on the 12z GEFS after mid-month. The Euro Weeklies had this to some extent on Monday.

The GFS is really banging the drum at 6z. Cosgrove on Facebook is mentioning a cold weather intrusion. There Holy Grail of November wx (for me) is a hybrid tropical system that gets entrained in legit cold front. Outside chance of that right now. That said, the GFS has been in error w/ that look at LR for about 2-3 weeks. However, that looks is now at d8-10. We know the euro struggles during shoulder season. At the very least, the GFS is now leaning towards a cold shot late next weekend. Weather is just a wee bit more interesting than it was a few days ago...

Now, let me explain. There is a tropical system approaching the coast around d8-10. If it gets caught in a front racing eastward, we get the KOD(kiss of death) early season winter storm that models have been trying to cook-up for weeks. Something to keep an eye on...but the 18z GFS is almost exactly how that might occur.

The 18z GFS is flirting with greatness.

CFS v2 18z is seeing a similar trough amplification after Nov10th. Is that the opening shot for winter? Maybe. Long way to go. I really think one good amplification would pop the ridge in the West and put the trough in the East. Ensembles aren't biting yet. That said, and I thought about this yesterday, shoulder season LR modeling is full of false alarms(both warm cold) during past years.

The 18z GFS is the way to a good pattern. Almost need a tropical system to jet up the coast and buckle the jet along the EC.

Yeah, seems like something similar might be on the table....

Just glancing at some super LR modeling, looks this indeed(the warmer weather) is a new pattern which (if you know me) I use a general duration rule of about 4-6 weeks(usually 6 weeks is my rule of thumb). Since this will begin around Nov 1, that would put the next pattern change around mid-December. Now, a pattern change could just be another warm pattern of a new variety OR a pattern which is only slightly AN OR one which is well BN. That would mean the heart of winter has a chance to be cold (mid-Dec to end of Jan) - I lean towards that. Only drawback is one cold spell during winter instead of two. Bookends of DJF would be likely warm. It is what it is. I would be difficult to find a more hostile Pacific in the LR. The only way I see us having a cold winter is if the blocking occurs in the NAO region. Though, I will ride with the idea that we will see 1-2 extreme cold shots, especially Plateau west, as that fits Nina climatology. Hopes for an early start to winter are dimming.

FTR, I do think we see a sharp switch to cold sometime in early to mid December to a cold pattern. I think this warm wx is a a 4-6 week pattern which is just beginning. Maybe the one positive to warm wx during November is that it may help with having colder wx over the holidays.

Nah....I take full credit for the massive warm flip in modeling. Just dig back a few posts and you will see the culprit post around Oct 10th. Hot take on my part!!!

We need a tropical/hybrid to break-up a potentially monotonous pattern showing for early-mid November. Big ridge building on most modeling, and might be quite tough to move once in place. My guess is that the pattern will flip on a dime as most Nina patterns flip quite quickly to winter. Anyway, summer-ish(early fall) like pattern showing for the first part of November. The pattern looks a lot like a standing wave(ridge) over the East. It gets knocked down but keeps most of the nation east of the Mississippi 5-20+ degrees above normal. The Euro control has some areas 30+ AN. I thought we might have dodged extended summer which is common with La Nina. This will be "extended summer", but without the ultra hot temps. We have had a nice Fall so far....warmer temps are back and are going to make an attempt to hang on. Bigger issue is the quickly developing drought in conjunction with warmer-temps.

@John1122, the 12z GFS has it yet again (different variation). That is a pretty potent set-up if it grabs energy out of the GOM at this time of the year. BTW, the GFS did pretty well with today's cold/snow at very LR.

Yep, indeed the GFS has had it between hour 330-348. As maligned as the model is sometimes(and rightfully so), it has an uncanny ability to catch some major events at wicked long ranges. Strat splits come to mind.

Fits our climatology fairly well. Seems like we have seen our first snow storm around halloween about 1/5 years. When I was a kid in Knoxville, that was unheard of. However, of late, early season storms have not been uncommon for the mountains. The GFS has been sniffing something out during that time frame for several days. It will be interesting to see if other modeling picks it up as it sits at 240h right now. I bet if we look back, the GFS might have had this from the word "go."

Last night's Weeklies and 12z GEFS seem to signal just a temporary crappy Pacific set-up (TCPSu) vs (PCPSu...permanently crappy Pacific).

Very familiar pattern on the LR GFS w/ a Hudson Bay Block but crappy Pacific.

Looks like a temporary trough amplification in the East, a transient(maybe 5-10 ridge out West), and then a more permanent trough in the East for November if the "shoulder season" Euro Weeklies are accurate. You all know the rules on that. That pattern would bring early snows to the mountains and snow showers to the valleys.