Carvers Gap

I feel like the 6z AIFS Euro (which just ran) is a pretty good representation of the 0z EURO and GEPS. Temps under that gradually cool to seasonal or BN. It is again worth noting that seasonal temps can get the job done from mid-Jan to mid-Feb, provided that timing is works (meaning not warm-up and rain). But give me that setup - all day long. EPO ridge, AN heights over Greenland and AO regions, trough north(or east of Hawaii), split flow. Trends over the next 2-3 days will be important. For now, decent chance at a good pattern in the aforementioned timeframe.

Now, I do think the following is possible. We have seen it show up on modeling but without overall consistency ->The cold shot around the 12-13th rolls into the Plains and hangs up over the East. It could hang up over the Ohio river valley, the Tenn River valley, the Apps, or even the East coast. If/when it does, an over-running event seems plausible. Beware the cutoff low over the Southwest. They are tricky, tricky critters. On rare occasions, they will simply set-up shop per the deterministic GFS, spin for days, and just burn out. But IMHO, they kick out about 90% of the time. If it were to set up shop there, when it kicks...the trough should still come into the East. Pay me now or pay me later. The good thing I can see on modeling this morning is the EPO ridge is present. That has not changed. When it reaches into Point Barrow, a cutoff OR split flow could develop underneath it. I suspect we eventually see both - a cutoff/bowling ball and split flow. Details twelve days out are going to be sketchy. So, I started looking at individual 6z GEFS ensemble members - it is the ensemble of the worst case deterministic scenario. I am not done yet sifting through the other ensembles. The 6z GEFS is not as warm as I thought it would be. I scroll right on down to Jan13...and then 14th. Remember, those are BN temps during our coldest climatology. A good number of those troughs stall. That tells me the risk for over-running is very high. If I was sitting in middle and western Tenn...I would want to keep an eye on this, even E TN. I can't get individual 500 height panels for the US, so I resort to looking at the temp maps above. Below is the 500 mean map for the hour above. The individual members tell a different story. Many of them must have kicked the trough eastward as the SER is squashed on roughly 2/3 depending on your definition of "squashed." Many of those cold fronts stall somewhere over the East. Knowing that SW bias is possibly in play, we take that 500 map and run with it. The EPO ridge has blocking over the top. Below is the 12z trend map for Jan 12. It looks like that for the rest of the run which implies the ensemble is correcting eastward with the trough.

If you look at the 6z GEFS at 500, you can see a possible feedback loop start at 276....seems not realistic at all.

Model feedback has been a huge problem all winter. Honestly, I have never seen the over amplification this bad. Repetitive Baja lows, repetitive NW lows, and maybe now repetitive Four Corners lows. One low is generally plausible - if we start seeing slp reform over and over…that is more than likely feedback. I start tossing model runs at the hour that occurs. If we see the GFS correct to an eastern trough as we get closer…it will make me wonder.

I suspect we are seeing feedback over the SW which is a known issue w modeling. Now, an actuall cutoff low could be legit under that big EPO. That seems impossible to have a cutoff under the ridge, but it has happened before. But given the massive amounts of model feedback and infinite loops this winter, I suspect that trough kicks right on out. By ~Jan 12.

I think the GFS is out to lunch. It has been all winter. I guess a broken clock is right twice a day though, and I won’t discount it quite yet. It has some support from the 0z GEM, but the GEM ends before the transition on ~Jan12 is depicted on other modeling - the GEPS kicks the tucked in trough out of the West right after 240. Eastern trough looks on time on the 0z Euro, every nonGEFS ensemble suite I can find, and the AIFS Euro…even the AIGFS to some extent. The ensembles have not budged overnight…EPS, GEPS, AIFS Euro, AIGEFS. Roll with them at this range. Check ensemble member counts. As I noted yesterday, the main concerns are cold source regions and if the ridge continues to retrograde (doesn’t stop in the West or eastern PAC). It could be the MJO is trying to gain same amplitude…but it has been so inaccurate this winter I am not using it a ton - yet. When we switched to the chinook in late December, modeling projected the event to start right after the 10th. It took another 12 days before it actually showed up. I think the same thing is occurring here…just with the cold. If non-GEFS ensembles begin to move…that is worth paying attention to. GFS verification scores have been terrible of late.

The 18z AIGFS is straight up frigid. Let's continue to keep an eye on Jan 12th. If we can get that down to roughly 7 days, that may be a legit time to track something decent. That run had a decent snowstorm for middle and west. My main concern is this...if modeling, which has tended to under model cold fronts(exception Jan 2), then that cold could be stronger than shown.

I think it is also worth noting that NE TN and SW VA may well see some snow in the air tomorrow if the 18z RGEM is correct.

I am not convinced of the correlation between phase 6 and cold. What I think is occurring is QBO induced HL blocking(in some cases) is simply prevent the MJO signal from having influence over NA. I think the MJO has a much bigger impact when HL blocking is absent. As Cosgrove noted, the best thing we can do is simply look at the vortices lined-up which are approaching the US. You can kind of see the stormier patterns and deduce timing of such. Use analogs to fish out a good 500 pattern in addition to wx models. That is more accurate than relying on simply teleconnections which I am always guilty of...

So, when I look at that. I see an East African/IO wave working from 1-2 to 4-5 and then to 6(and then fizzling out). I also see some convection at the dateline which is phase 8. Looks like the phase 6 dies out. In my mind, that would correspond to the warm waves prior to the 12th per lagged composites? Looks pretty weakfish to me in general with 2-3 strong days in 6. I think HL blocking eventually trumps it unless it holds onto that stronger look for more than 2-3 days.

Pretty good looks in my book. I used to only do long range stuff based on precip anomalies and temp anomalies. I don't think I am much better today with all of the extra stuff. Here are some Euro LR ext maps centered on d15-46. I have attached both the mean and control runs. You can see below normal temps with above normal precip(yeah, that surprised me). I actually went through and looked at the precip by 7 day increments to see if it was just one big rainer. Nope, it looks like normal precip with the exception of the first maybe ten days. BN temps, AN precip, and a solid 500 map.

Thanks for that info. I was having a hard time reconciling what look like really cold maps with that phase. I know there are times when the MJO has less influence.

The 12z EPS looks like a washed out version of the deterministic which I posted a few posts back. Good trends.

The green is convection, right...or is it the brown?

Here is the 12z Euro d10-15 pattern. The noticeable difference is Alaska. That Bering Straits low floods Canada with Pacific air. While it does have precedent, I think that feature is likely wrong. Get that our of there, and it is the GFS 12z run. IMPORTANT: What we are seeing(and this is under way even today) is a retrograding of the eastern North American ridge into the eastern Pacific. How long does it stay there? IDK. It could keep retrograding. But it is wild to watch the ridge get knocked down, and then "resurface" further west. How that ridge retrogrades is going to be key. A retrograding pattern has often been good to us regarding winter weather.

This is a pretty good trend from an albeit not-the-best model of reliability....This d11-16 5d map from the 12z GFS. That is a big time winter pattern if it verifies.

Who knows if the 12z GFS is right or not. I certainly don't. But for the sake of discussion...if that cold front comes in at the angle and slow speed that it does on that run, that is prime for over-running sometime after the 11th. We have seen that repeatedly during the past few years with Nina winters.

The January 3rd slider which is rain...The 12z Euro has frozen precip at higher elevations in the Apps and in SW VA(northern sections). Temps remain in the upper 30s and low 40s most of that day. If that moves in at night...we could see some snow above 3000' IMHO...maybe lower. That is a sneaky system.

The 12z GFS(so proceed at your own risk) has a monster Alaskan block by around 300. So far(famous last words), the pattern at 500 is moving forward with time.

I still think we are right on track for right around Jan 12. I would not be surprised to see it speed up or be delayed by a day or two. I also think we will have some minor chances prior. Models have not been great w/ details or seeing cold fronts this year. They flip around a lot. We go through the same thing every year with the same complaints. Sometimes models are simply too quick with the pattern change. They also really struggle with the NAO. Let us not forget they lost the pattern change in early December only to add it right back after 2-3 days when the pattern emerged from the 5-7 window where things get lost. I am not saying that happens this time, but it is worth considering. And no Icy, the pattern is not 16 days out...but I think you know that. There are no guarantees, but roughly timed, the EPO starts to build on the 8th-9th. The 12z AIFGFS(admittedly not an overly reliable model) has the beginning of the pattern change inside of 240 hours. In fact, I can make a pretty good argument the pattern change is underway now w/ the big -NAO which "should" retrograde into the EPO block. In my mind, we lost a 1-2 cold fronts in the pattern w/ the cold sliding to our north. Phase 6? Maybe and sure looks like it. The 12z GFS also has the ridge building into the eastern PAC around Jan 8th as well. I was showing maps last night, because quite frankly...I was trying to stay awake which I halfway noted....turn and burn to Knoxville. As noted the GFS (which has been truly awful this winter) had some phase 6 stuff yesterday. I haven't looked today. MJO plots at CPC have been largely unreliable this winter as the MJO has just flatlined. The driver going forward is likely HL blocking, but there will be a likely transition in order to get to that point. The biggest thing is to watch the 500 pattern and see if the EPO ridge keeps moving forward in time. If it does, models should trend colder. It looks to me like we are going to have to roll one ridge through the eastern pattern from Jan5-8th. I will check back in a bit. We rolled in last night at 3:00AM. Just catching up.

Haha. You are lucky I was posting maps at midnight to begin with. I normally don't do the (model) night shift. You're welcome. They are free, so you get what you pay for around midnight......

Nothing burger from the 0z Euro. I have read some conversations that the MJO rolls into phase 6 right as the EPO forms. We may be seeing some of that. The Euro at 500 is still better than 12z though IMO. See u at 12z tomorrow.

Nice looks and decent agreement in general with cold placement and vastness of the airmass.

Sitting in Knoxville… The 0z AIGFS is definitely quick with the EPO ridge as it installs it around the 8th, and the trough begins to kick eastward at that time. Very cold model and the 0z GFS has basically joined it. John covers all of that nicely above.

I am also noticing at tendency on the 0z GFS to include split flow with the -EPO.