Carvers Gap

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.

The 18z GFS was straight cold. Winter is here. There will be some brief warmer interludes...but looks like it is going to be cold for a bit, especially centered around the first week or two of December.

Pretty steady snow in KPT. Looks like Morristown is getting the best of it. Any reports from down that way?

Snowing at Boones Creek near JC.

The 12z ensembles are still very cold. There are days twenty degrees below normal embedded. No single storm has been zeroed in upon. If anything, modeling is a bit colder and drier today. I have a feeling we see frozen precip though. Patterns looks really good. Lots of virga IMBY at the moment. Wind is cranking and it is appropriately cold for late November unlike the endless summer which has thankfully and abruptly left us until another year!

Probably one more question as the 6z GFS has this scenario... 5. How long (if at all) does the SER keep the extreme cold at bay? This reminds me a lot of the setup which led to the historic middle and west TN (and also MS, western KY, eastern Arkansas, maybe Mizzou?) overrunning event a few years back. I tend to think the cold gets to the East Coast even if a bit modified. The source regions for this cold are cold. This isn't Pacific air. I wouldn't even call it Canadian origin. This is from up top.

The 6z GEFS ensemble is about as cold as one can get at this range. Some questions that I don't have the answer to regarding this cold air intrusion... 1. Duration of the event? Best guess is very late November into mid-December, and maybe right up to the week prior to Christmas. Then we see a thaw o sorts. 2. Does the pattern reload with more than one cold air mass or is this just a 7-10 day cold shot, and then done ? 3. How much frozen precip falls? There is certainly an active precip pattern predicted. I think the risk of an overrunning event for middle and west TN is increasing. However, an ana front like we saw at Christmas(but not Christmas this time) a few years ago is probably also on the table. 4. Does winter return(if it arrives) after December? Big question w/ lots of differing opinions. With the ENSO forecast busting badly, I think that will cause some unseen downstream forecast problems, especially in LR ext modeling(as it continues to change in order to handle the new SST data). The climatology changes IMHO if this is a very weak Nina. My original winter forecast....climatology might not apply. Weak Nina climatology argues for a mid-winter thaw, and then more snow and cold later in January and early Feb. For now, I remain cautiously optimistic(if one can say that given the human suffering left by Helene) that winter is on its way, and that some in the forum area will see wintry precip. This season I do pause a bit with the celebration of the return of winter. I know folks in the mountains are in a tremendously bad spot - roads, homes, heating sources still being put into place. The good thing lately is that it has been dry, but extreme cold would add insult to injury. Hopefully responding agencies are looking at longterm forecasts for December, and are moving heat sources into place. Those warm interludes between cold shots would definitely be helpful. So, if it gets warm at times during the winter....it is probably appreciated by those impacted by Helene. Mountain people are tough though. They have lived through severe cold before. On a final note, I know JB talks a lot about late season hurricanes being correlated to December cold...that looks to possibly verify. Some of the cold showing up on modeling would be cold even in the middle of winter.

Surface pressure (Euro Weeklies ext) is very much EPO driven. Cold goes down the front range and spread quickly eastward. The only thing to watch is if modeling tucks that trough under the EPO ridge into the Mountain West. That means cold would come down the west slopes of the Rockies. However, I feel given the time of year that the cold will drain down the front range and race eastward. This is a cold and storm pattern. Precip is normal to above for the forum area during December. This would allow for a January thaw and potentially winter returning later in January. It is a good thing that we are seeing this in November as the winter will often repeat November patterns. This is a 30 day map! That is Alaska cold with a great mechanism to get it south eastward.

This is pretty cold for a 7-day ensemble at range. That means reality could be much colder. Almost 20 degrees below normal at this range is a big number. Now, this could change, and we have seen these looks evaporate or just be a 7-10 days too early. Something to watch, but super impressive. That is an overrunning look if I have ever seen one. Somewhere between I-40 to the Ohio River looks like it could be the track.