Carvers Gap

The Euro Weeklies look like they have for the past 3-4 weeks which is cold weeks 3-6 w a warm up at the very end. They were prob a bit quick with the pattern change. They are about two weeks delayed from the original cold looks of a few weeks ago. For now, I think Dec 10 to just a few days after NYs looks BN for temps. For snow lovers, the concern would be cold and dry. The good thing about a +NAO is that the Gulf would likely be open for business. Could be warm up and rain…just have to time it with some of those inevitable highs coming from the prairies of MT. With a potential for SSW…we could see the cold hit 2-3 weeks after which would be an extension of cold into Jan. Model chaos on the horizon indeed.

IMHI, it really isn’t a Texas Blue Norther. That Euro cutoff partially pumps a ridge which locks all but the northern tier out of the cold during the first week of Dec. It is the Four Corners cutoff which drifts southwest into Baja and slowly runs out of steam…that is the pattern issue in my book. I am fine with a SW cutoff which eventually kicks out - pay me now or pay me later set up. The slow stall and drift into Baja is the thorn. The good thing is most ensembles get to the same EPO/PNA ridge setup by ~d14. The NAO(chuck mentions this in the MA) has gone poof, and that doesn’t push BN heights(over Canada) as far south as originally prognosticated. The Weeklies are only half completed as I type. I see Jeff has posted. Gonna hit enter and read it.

I mean really this is just a repeat of the start of our past La Nina winters for the past decade, including the model delay of cold air. What I am really interested in is this....With this shakeup on modeling, does it displace the entire pattern cycle by at least 7-10 days IMHO??? That may well leave us cold to start January - maybe.

There should be some wild model swings, but we are gonna have to let the dust settle after the past 24 hours of models flip flopping. They may go back cold like the AIFS. They may trend much warmer if that cutoff is really. So things to watch? Does that cutoff leave the SW or does it stall out? If it cuts of and stalls -> SER here. If it ejects -> big time cutter w/ cold following. Until that gets worked out, just guess work.

I had a ton of posts up this morning, but as I dug through modeling one thing was clear...ensembles and their deterministic runs were signaling a big warm-up after the Thanksgiving cold. How long does it last? IDK. In a rare move, I deleted all of those posts. Why? When modeling moves in unison towards warm...something is afoot and it usually isn't cold. The MJO argues for a very sharp cold trend in LR modeling which is not present yet. Sometimes, modeling doesn't "see" the MJO until about d10-12. The problem is the MJO really doesn't drive winter weather until Jan/Feb...and maybe late December. Right now, everything is very volatile after d10. Extreme cold is still on the table but kicked to December 8th or later IMHO. Outside of experienced mets, nobody knows what is coming w/ that cutoff low and SSW projected. An amplified pattern appears likely with wild swings between cold and warm.

Yeah, sure bet SSW is wrecking havoc on what looked like a good pattern without it. We have seen this many times during the past winters -> good pattern at range gets wrecked by an SSW. The only positive with an SSW is that it could put very cold air over the eastern US. My guess is that it dumps into western Canada and Montana and SLOWLY oozes west over a period of 1-2 weeks and modifies greatly. The big thorn in the medium to LR is a cutoff low over the SW which dives into Baja to start December. Until modeling works that out, the EC wx pattern is probably wrong. If that is real, that will pump a monster SER over the SE. There is ample precedence for this. Sometimes modeling is correct. Sometimes it is feedback. The 12z Euro goes absolutely bonkers with it. It creates a chinook over the southwest which pumps record heat into the souther half of the United States - like summer time heat for early December. I have looked at major ensembles today at 12z, and they are just wrecked. No other way to put it. What do I mean by that? Consistency is just shredded. In "general," the can has been kicked by a week at least. The Weeklies caught this first. I may just start using the Weeklies...LOL. However, the MJO and ensembles definitely foretell of a huge trough over eastern Canada by d14-16. Problem? The SER is flexed big time, and that standing wave is gonna have to get knocked down w/ several cold fronts. It cuts the bottom out of the trough. Seasonable cold looks like the outcome if today's iteration is correct, and it probably isn't. Let's hope the EURO AIFS and GEPS are correct, and they could be. For now, I am kind of watching the timeframe just after Thanksgiving. I wouldn't be surprised to see a NW flow event or storm pop w/ that. 500 vort maps are not missing by much when it comes to both streams. Overall, I think the cold is coming, but any time models start "can kicking" in unison, be very careful about expectations. I wouldn't be surprised to see a record cold outbreak. I wouldn't be surprised to see it completely vanish at our latitude. My gut says extreme cold is coming for the Mountain West. Why do I think this? 15 years of watching it do that 90% of the time. It will make its way here probably between Dec 10-25. Then we warm up. I suspect the cold reloads quickly and we see another bout to start the new year. While I am bearish now for early December, I still think we see a reloading cold pattern which is prob the result of the SSW. But for now, I am "out" on early December extremed cold. I think it will be seasonable to AN for week one, transition week 2, and maybe a cold week 3 before warming back up...and reload.

What is even wilder, a lot of higher elevation folks are already on the board. I am even on the board w/ 0.5" of snow already, and w/ a NW flow event to boot!

The mean doesn't have dump into Texas. In fact, it might have the trough too far to the East. Right now(and I know you know this...but this is for new folks), it is so tough to know the trough axis at this range - IDK at this point. Some modeling is just sending the cold straight to Texas. Some tends to send into the SE or NE and the MA. I would suggest the MJO is driving that along w/ the SSW. If that MJO stalls, we all will probably be just wanting it to warm-up. In my mind, I see a cold shot after Thanksgiving, a warm-up, another cold shot around the 3rd which means business....and the cold keeps on coming until about Christmas when the pattern moderates. The danger is that some modeling does not want to moderate after Christmas. There is a small camp of model runs which deepens the cold to enter January. In fact, seasonal cold is the warmest those runs get w/ well BN being the base pattern. Now, I hate even to mention that on a forum. If it doesn't happen, the disappointment is tough for some....and that hasn't happened since maybe 09-10 But it is worth noting. Those runs aren't quite outliers either. The MJO above would support some of those runs. The interesting thing is if the MJO were to loop back into the cold phases w/ no tour through the warm phases...we haven't seen that type of plot recently. Plus, there is the rare tour-de-warm MJO that never gets warm. This is IMHO is class -QBO territory in terms of analogs.

Precip is AN on the mean and all over the place on the control. The control implies good precip for western areas of the forum(remember the boundary) and then again for coastal areas from Georgia to the MA late in December. E TN and W NC would be BN for precip if the control is correct. If the mean is correct, the entire forum is BN w/ temps and AN for precip. I think the cold is under modeled at this point - I didn't think that a few days ago and my mind can change on that again. If it is, the storm track is along the spine of the Apps.

For now(and famous last words as we have been fooled many times over the years by December cold on modeling which didn't verify in reality), there is a decent signal for a cold December. Will it be stormy? Well, we honestly maybe don't want the severity of cold shown, but the opportunity for NW flow events and for Gulf systems to attack the base of the trough are probably embedded in a pattern like that.

Here is the Euro Weeklies 30 day map centered on December(the above is Dec3-Jan4). This one is Dec1-Dec31. I have also included the CFSv2 which ran at lunch. Where that EPO ridge sets up in the eastern Pac is important. HL blocking near Greenland is not as important in December as it is in Jan/Feb. But it would only accentuate potential for cold. As John noted, the real risk is cold/dry. The good thing is that models are showing some AN heights over FL. That would imply that rain/snow would run a path from say TX/LA to DC. Storm tracks could be the Ohio Valley if the pattern relaxes or the Piedmont if the cold presses. edit: the slight area of an heights over the Gulf states is not a bad thing. Overall, temps in our area are seasonable BN. The storm track will likely ride that boundary. I suspect(if the mean is correct), MUCH colder temps would head southward. That EPO ridge is nearly perfect for sever cold outbreaks.

I have like the Euro control of the weeklies. Meaning that if the ensemble and the control don't match, that is a problem as the control is often right. It spotted the push back on the colder temps for early December. It wasn't completely right, but there was a warm front embedded that the ensemble didn't see. This is this afternoons December map. I don't use these maps verbatim, but just to get a general sense of what is on the table if the 0z Euro was run past 16 days and all the way to Jan 4th! The ensemble shows this general depiction but MUCH more washed out - seasonably cold. It is also important to remember that seasonal cold at range...is probably colder in reality. -15F departures (relative to norms) is insane for a 30 day map. edit: To me, that is showing signs of the stratospheric warming as the latter part of that run is brutally cold in the lee of the Canadian Rockies. We see that often w/ strat warms. Cold dumps west and spreads east. The last week of this run is almost 40 BN in the Rockies. Notice those aren't reflected strongly on this map...it had to eras some warm departures in those places.

MJO stuff...First off, that is not a warm look for December. In fact, it kind of just crawls through the left side of the plot which is not something we have seen in recent years. It seems like the MJO almost defaulted to 4, 5, and 6. How many times have we seen the MJO hit the wall in phase 6 and not move? It looks like this time it might hit the wall while in the cold phases for once. That "could" mean an extended period of cold. If you like really LR thinking, I have to wonder if it can get through the warm phases(before winter fades) if it exits the cold phases in late December or early January. I think it can...and probably by the last third of January. That would give us two decent shots of cold if one assumes winter comes back during that last week of January. But that second cold shot can be difficult, but the QBO may help us in that regard.

It will change, but the 6z GFS shows the potential for the pattern with a slider late in the run.

The 12z GFS and to some extend the 12z CMC were flirting with an anafront. Worth watching as most modeling is now "seeing" this earlier cold front. Jeff mentioned it in the December thread. But I guess we prob should put the actual storm here(if it occurs).

I don't really do hype. I know the winter weight which Dec 2009 carries. The CPC has been using it to balance out their analog package for a few days. I doubt the entire winter matches this analog, but December(at least the first 2-3 weeks of it) looks like a decent match when compared to ensembles and some LR ext modeling. Kind of uncanny. Two different models with similar outcomes in regards to analog matches. In all reality, those are just MJO matches vs actual analog month matches. That said, pretty sure the QBO was dropping or negative during Dec 09-10.

12z CMC ensemble when compared to the surface temp map of Dec 2009.

Some fun stuff. 2009 has been showing up on the CPC analogs for a few days now. So, I thought I would look at the Euro Weeklies and the 2009 500 map. I centered the Euro Weeklies map on d10-40. If I go five more days, the BN mean shifts eastward more. Some differences, but a decent fit overall. We know what happened after Dec 2009. I threw in the GEFS MJO for good measure.

Ok, you all made me break down and look at the MJO. I really hate looking at that metric. LOL. Well, on pretty much every model it crawls into 7(sometimes 8), loops, dawdles, and stalls. 7 is cold when centered on NDJ. 8 is colder. It certainly looks like, as John and Boone and others have noted, that LR ext modeling is being driven quite early by the MJO. That probably is a good thing considering the MJO is in prime real estate by the end of the month. When it actually arrives into 7-8 is open for discussion. Nearly every model gets there w/ the BOMM and EMON being optimal. It just doesn't want to leave the left side of the MJO plot.

Update.....

The 12z Canadian has similar set up in terms of cold. I would not be surprised to see an anafront system develop if the cold is that strong. The AIFS is 3-4 days later. Modeling is picking up on a strong cold front...timing TBD. The Tenn-Vandy game would be pretty frigid if the 12z GFS/CMC were to be correct.

The 6z Euro AIFS has some company.

Well, well, well...look what the 12z GFS just drug in.

6z Euro AIFS FTW....been wanting to post that all morning. Cloudfare had other plans. Thankfully, systems are slowly coming back online.

D8-14 analogs from CPC today. Really pulling for the Dec 09 thread to be THE analog. 19851121 19561203 19851116 19721207 19641123 20051202 19961113 20081214 20091207 19801203