Carvers Gap

The 12z GFS is cooking something up around 180.

I think operational modeling is under-doing d8-16 temps.

For now, I am sticking with ensembles in the d7-16 range. Operational modeling has trended warmer for the past couple of days. Wild swings like that tend to signal very cold air beginning to work its way into the pattern. That type of low level, Arctic air wrecks complete havoc on modeling. Ensembles OTH are quite cold with little change to the EPO ridge and downstream EC trough. I thought I would add the graphic below just for kicks and giggles. This is the Euro control from the Weeklies run this afternoon. It probably doesn't have much(if any) skill. But what is interesting is that if North America gets that cold, the MJO won't matter nearly as much. It will simply mean "less cold" as it goes through warm phases, i.e. just different variations of cold. One final note, modeling will often be too quick with cold, and then bring the hammer later. The above map shows "what could" happen as we see a very La Nina temp structure for North America, but cold just overwhelms the pattern. It has been a long time since we have seen cold that encompassing over NA. Again, it is just an example of one pathway that the weather could take. There are many, many options on the table for that timeframe, especially at this range.

I concur.

Good info. JB says the MJO warm tax will have to get paid after Dec 20. If the Niña comes to pass, prob more cold finds its way here per JB. Typical Nina winters have periods of warm accentuated by severe cold.

Thanks for the info on the AIFS. I have been meaning to ask how good it is. I never know what to think of it. It has a little bit of DGEX in it, but it has been really decent during the recent weeks I have been following it - I really have just started to use it.

The 12z ECMWF AIFS is picking up on a really cold shot around the Dec 8-10. That would be a second very cold shot in addition to the Dec 2-6 timeframe. The CPC maps this afternoon are dark purple for temps for this area. Apparent temps during the second cold shot are showing up in the single digits for valleys and below zero for mountains. I would almost think and ana front is probably going to be embedded within future models runs at some point. That cold means business.

Pretty clear signal in LR ext models of the ridge retrograding into the Aleutians, ridge tucking into the Mountain West, and SER establishing around the first week of January. Now, that is a LONG way out there. However, that fits climatology and fits the recent Nina winters. I have my suspicions as to whether that can hold long term. It is likely a January thaw with winter returning later that month. This pattern coming up has an almost extreme EPO ridge, and that is not sustainable as a long term pattern. The ridges and troughs need to be flatter. JB mentioned today that there should be some upwelling of cooler water in the ENSO regions which should bring La Nina into play. We want that. We don't want a Nada which is "dud winter territory" for this area. If we can get the weak La Nina, I think we see more cold later in winter. For now, it looks like cold through roughly December 20th(give or take 3-4 days), then seasonal as the trough retrogrades, then a return flow from the GOM due to incoming HP, and then a great big question mark. So, I think we have a pretty good idea of cold duration now. I think!

12z Euro AIFS set to go boom...that would make a lot of folks happy who have been watching the rest of us have fun for several winters.

The seasonal CFSv2 from this morning...EPO and AO driven it appears to me.

Awesome. And that is what I was thinking that might be....it is all over the place. That means IMHO that there is above normal uncertainty for this winter. I "think" we probably can get rid of the warm Decembers...at least through Christmas anyway. After Christmas, maybe a switch to warm pattern or a brief warm-up. I can't tell at this range. It is interesting that we aren't seeing a lot o 2000s analogs with that, and that is interesting. Either they try to factor out recency bias with their analogs, or there is a thought process that this winter is not fitting recent analogs. I don't know the answer to that. The potentially cold start reminds me of 09-10, but I don't think it matches the ENSO state. I will post the CFSv2 from this morning(likely suffering from feedback for Jan-Feb), and if it isn't actually suffering from feedback...that is not like many 2000s winters. Maybe 14-15? Maybe 09-10? Could be something and could be nothing. The CFSv2 is a flavor of the month model for me....changes a ton. However, American modeling does well enough at very long range that I do pay attention, especially during early winter.

Sorry. I should have specified the non ‘89 winters. I was at UT at the time. We missed on a massive snowstorm.

Here are the d8-14 analogs for today from CPC: 19561129 19851221 19881208 20081130 19581212 20021128 19891221 19561124 19761124 19881213 Any thoughts on these?

Still very cold ensembles. The 12z GEPS is very cold. It makes me nervous, because it often catches the cold before other ensembles. If that verifies, we could be looking at severe cold incoming. The 12z Euro and CMC both at varying times have incoming winter storms. It is possible that the pattern is dry as the EPO ridge is so, so tall. That combination often forces us to rely on northwest flow events. Either way, buckle up. Wild pattern looks to be on tap if you like winter. I tend to think the Euro/CMC model group(once they "see" the cold) are formidable. The Euro was crazy, crazy cold at the end of its run. I am not so sure that isn't record breaking. I haven't looked.

Still not a lot of changes to earlier thinking. If anything the 500 maps of all three major ensembles continue to advertise a very strong EPO. I have to think that breaks down at some point, but modeling has it through d16. Even though Nina is still technically a Nada...The potential cold start to winter is very classic Nina climatology. It does look like the NAO is trying to fire. That is not surprising given that it has been more active during winter after going a couple of decades without much activity.

Good thread. I may read some more of his ideas tonight. Good share!

Day 8-14 CPC analogs from yesterday. Triple weighted '89. Interesting to see an 09-10 analog show up in there - not a La Nina nor a La Nada analog, but a great winter nonetheless. I would be interested to learn how that made its way into that analog set. 19891218 19631213 19581210 19891213 19551129 19891208 19561201 19581205 20091208 19761202

Still a little bit of meat left on the summer/fall thread bone. Blizzard warnings are posted in West Virginia. We don't see that very often during November. Winter has arrived.

But ya'll, I love this kind of weather. It is cold, windy, and spitting snow. After two and half extra months of summer, glad the switch finally flipped.

We ended up from a dusting to a 1/2" of snow. I drove through almost convective bands last night and this morning. Definitely a nice event to start the season.

Nina climatology often supports a cold end to November and cold December. Then, it warms with diminishing chances for cold in the western forum areas. That is the bulk of climatology. However, there is a group of analogs for weak La Nina years which produce very cold winters for almost all of the forum areas. They make-up about 1/3 of weak La Nina analogs and most of those years are the benchmark winters for the Tennessee Valley. I am not saying those are in play right now, but I can't rule it out. I suspect modeling is falsely perpetuating the eastern trough past Christmas, but there is is about a 1/3 chance that this winter could be "base cold." To quote Ben Kenobi, "Now that is a term I haven't heard in a long, long time." It should be noted that the collapse(or lack of occurrence at all) of the La Nina was poorly forecasted. ENSO forecasting at range can be bust city. So, with the ENSO state being a bust for this winter...that opens the door every so slightly for a colder winter due to weak La Nina climatology coming into play. Again, 1/3 is the ratio to remember. Many of us have noted that we are a bit uneasy about this winter's forecast, because those analogs are the opposite of the other 2/3.

And this is why January gives me great pause. This is from my winter forecast. I haven't looked, but I bet the PDO this go around is less optimal. However, this is part of the reason that I am less confident than I have been the past two winters.....Again, I lean warm for January, but there is precedent for a much different outcome. I am going to go ahead and add these. And I am far, far deeper into this than intended...Sorry, this is kind of a "stream of thought" post, and maybe not as scientific as it should be. I also want to add 16-17 into the mix at it was a first year La Nina and should be weighted equally or more to 17-18. But here is why I am far less confident this winter. See the 94-95 moderate Nino listed in the graphic at the very bottom of this post. This past winter reminded me of that type of winter - blah and not a lot of chances. Now, what came after 94-95? The winter that shall not be named, because I just won't invoke a winter that is a benchmark winter of my lifetime, and it was true winter. It was a weak La Nina following a moderate El Nino. It is also a winter that maybe doesn't fit the current warm basin look of the Pac which is why I haven't used it. That said, it might deserve some weight though I haven't given it any. Just beware.

Just for kicks and giggles. This is the CFSv2 seasonal control run for January. Take a look at the cold analog package for January in the winter spec thread...and look at this.

This is what I look at when I am looking at modeling in the long range... Image 1: Euro Weeklies Control 30d 500map...What could go wrong, but what I don't think will happen. Referring to previous winters and not this set of model runs....the trough tucks out west after several dozen runs on LR ext modeling of it being in the East. There is precedent or that during past winters. Basically, we have followed severe cold for weeks on the weeklies, and at the last minute it dives west of the Rockies. Again, I don't see that right now and the ensemble for the same model doesn't depict that at this time. Image2: Euro Weeklies ensembles 30d 500map....Looks about right. EPO ridge dominates and then retrogrades westward. How far it retrogrades to the West will be a big factor in how long it stays cold here. Image 3: GEFS ext 30d 500map....Please note it doesn't go out as far as the Euro, but still....not bad. Image 4: That is the CFSv2 from this morning for December, January, and March. It probably is dealing with a bit of feedback - meaning keeping the trough in the East too long. However, some of the analogs in my winter forecast have exactly that, so I can't discount that. Big EPO ridge during Dec-Jan. NAO pops in Feb. I noticed Cosgrove mentioned that his winter forecast has been cooled down a bit to reflect the early pattern of winter and more cold intrusions than originally thought. Right now, January is(and has been) a bit of a mystery for me. What we are seeing could just be classic Nina climatology even though we aren't at Nina thresholds. We could still(and I think we are) seeing Nina climatology reflected at the North American surface as evidenced by the warm fall and flip to cold during late November. If the CFSv2 is even half right, we take that and run. If Nina climatology is in play, we should see LR ext modeling warm for much of the rest of winter. Remember, LR ext modeling had December as warm before it flipped cold...Nina climatology won out. That said, and I sound like a broken record, there are two very different paths in analog packages for January. Either fits climatology. That sounds like a cop out, but that is the lay of the land. I still tend to think Jan-Feb are going to be warm. But if you look at my winter forecast ideas, I noted that January is sketchy and that gave me pause for that month. I have two sets of analogs built or that month, and they are very, very different. Even Mark Reynolds on the WJHL11 winter forecast noted that there are two different analog packages for Nina winters. If this goes to a weak La Nina, that is a significant development towards having a colder winter forecast than I have listed. Technically, I can still change my seasonal forecast as it isn't meteorological winter. However, I generally go with the idea that first ideas are often correct, and only change if certain you are wrong. What I think I potentially have correct is that the pattern would flip cold during late November, and that winter starts cold for December.....So, that is tough for me to change since those ideas "seem" correct so far. To be fair, December hasn't occurred, and there are no certainties in weather forecasting at this range. But those cold looks for January could flip warm IF the warm set of analogs turns out to be right. My lean towards a warm Jan-Feb is diminishing though with each passing day. Part of me wonders if the base pattern is the trough in the East??? That said, you can see the SER fight the cold over the southeast, so I think the SER will be a player. More later.

The ensembles have a very cold pattern to start December. We are going to see a lot of variation in modeling. Last night's snow was lost between d7-10, and then very slowly came back on modeling. I don't see a ton of snow on modeling this morning, but let's see how this begins to looks as it gets into range. A rough window is November 30-Dec14. Big questions after that whose answers mighta allow us to squeeze a couple more weeks of less extreme cold out of that pattern. One warning(and I don't see this yet...if anything quite the opposite), sometimes modeling will be too quick in bringing the strongest cold. Right now, ensembles are about as robust as one can get at 500.