Carvers Gap

After seeing the Sierra Nevada this summer and seeing the deep snows from forecasts and webcams...we started talking about the Donner Party. They got stuck north of Mammoth Lakes and Yosemite National Park in a place just west of Lake Tahoe. I never could understand why they didn't turn back once it started snowing. Once it snows 4-5', you really are stuck without modern machinery or unless a thaw occurs - I understand now why they got stuck. Really, there was nothing east of the Sierra Nevada at the time (to over winter), and other than grass meadows(where Reno is now) there was no place to wait until spring. There "point of no return" might well have been Fort Bridger. Once they crossed the Wasatch, they were committed. If you are interested in the story(and it indeed mentions the MJO of all things!!!), The Indifferent Stars Above is a great book. It is not for the faint of heart due to the subject matter, but...it provides a riveting story which begins in Illinois, covers each section of the trip(from Great Plains to the Sierra) and ends just short of Johnson's Ranch. There is debate on how bad that winter was. Some say it was a low water year. However, the photos of the stumps in that camp were cut nearly 20-25 in the air. It is likely the snow was incredibly deep, but water content low. There were roughly ten winter events that winter, some from atmospheric river episodes. Winter came early that year, and by some reports, even the hills above San Francisco saw snow that fall. Winter, for sure, came early that year. It buried the inexperienced travelers(at least inexperienced in winter camping and survival). What came next is one of the most horrific narratives in the American settling of the West. Amazingly, some of them walked out during the dead of winter. I though most died in that bowl of ice and snow near the summit. Nope, roughly half survived. 2/3 of the men died. Only two single men survived. Larger families survived.

GEFS trends from 0z to 18z. Pretty big moves.

The 12z EPS and GEPS have this as well. AI models can be sketchy for sure - completely unknown. I am not sure they are actually "learning.". I like the EURO AIFS better than the AIGFS(seems not overly rigorous) FWIW. The 18z GEFS continues to trend the rest of the other ensembles w/ the eastern trough. The good thing is the EPO ridge moving into position is almost 7 days out. I will feel a lot more confident once it sets up shop. The NAO has verified as pretty strong...so good sign modeling is handling blocking well. We have definitely tracked patterns which fizzle. Let's hope this isn't one of them. We have also tracked many patterns which eventually verify. Good info on the ENSO and PDO regions - thank you!

The actual EPO is to supposed to build Jan 8-9th. So, that transition is well within ten days. Right now, that ridge building starts at about 180. The transition to that ridge is arueably occurring now.

The 18z AIFS Euro ensemble is pretty much awesome. Big ridge out West, and big trough over the East. Makes sense.

The deterministic GFS over the last four runs has shifted the 500 pattern about 500-1100 miles eastward depending on the feature.

We will see. The GFS is relying on the ridge being over the East and return flow from the Gulf. The trends right now are bit time towards a trough over the East on that model. That model is incrementally caving IMHO. If so, the trend would be much more dry.

The great thing is the 18z GFS seems to have figured out that the trough has to kick out if under an EPO ridge like that. Just wait till 0z, we will have something new! Haha.

The EPO ridge hasn't been delayed as of yet. We lost a couple of cold fronts on the 4th and 8th. This has been moving pretty steadily in time. But we all obviously know the rules. Most of the folks here are pretty solid veterans when it comes to flip flops.

The 18z gfs is gonna give you whiplash. I just want to warn you now. You may need some Advil after this one.

Kind of a theme I am seeing in modeling during the past 24 hours...modeling is struggling w/ the NAO. Duration, strength, and placement are all an issue. I think we score the EPO. We need at least some weak positives over Greenland which would tele connect to cold in the SE and to a block over Yukon and/or Alaska. If you look at wild swings in a model, go look at Greenland...it probably changed at 500. For now, I am riding w/ ensembles and using deterministic models for trends. Once we get Jan 12-13 in range, we "should" (famous last words) see models produce colder solutions. Ok...on to Indiana vs Alabama. I have been looking forward to this one. SEC vs BIG.

This is likely over-done, maybe by a lot. Here is a 30 day Euro Weeklies control map. The Weeklies mean pulls the trough back at the end of January, and I think it relies too much on climatology with that look. Still the mean wasn't overly warm. Even on the mean, the cold punches back during the second week of Feb after a good 10-14 day stretch in January(mean). The control, however, keeps putting the EPO back in the eastern PAC. Again, this is probably too much...but it lets us see something that a washed out mean won't.

TRI will finish +0.7...so, basically normal. Interestingly, TRI had 19 days BN for temps. The 6-day chinook brought temps to normal. There were 9 days were a trace or more of snow were recorded. We had two days where we hit single digits. We had a high of 71 on Christmas. Two days later, the high was 33.

The runs d10-15 have some decent rigor in regards to the long wave 500 pattern. I think where frustrations occur(me included at times) is the details are often just wonky and getting wonkier - see 12z today. My main concern is that some of the solutions make zero sense. Prior to November, the solution might be wrong at that range...but at least it looked plausible. I am a big believer in getting the pattern right, and then let the chips (details) fall where they may. I am cautiously optimistic that we have a chance at a good EPO pattern right when our climatology is the best, beginning around Jan 12-13 for a TBD duration. I think we can use d10-16 maps to get a clue as to that pattern. Sometimes we will see a model lock onto a big storm at that range, and nail it...but generally only w/ big storms. I have seen the GFS nail two strat splits at d16....it has an uncanny ability to model the stratosphere at range, maybe not so much the surface at range.

Ensembles have all run. Generally (exception EPS since it only goes to d15), these are 5day blends of d11-16. In other words, we are taking January 12-17th. I have attached the 12z GEFS and compared it to its 18z run yesterday - flip city. Key notes: -The EPO ridge looks legit. WHERE it sets up is going to be important. -The 12z GEPS is probably the best case, but it is hard not to like the 12z AIFS Euro ensemble w/ that Alaskan block. -Now the 12z EPS is interesting. That is more of a PNA ridge. Likely feedback over Alaska w/ that trough. -12z GEFS is trending considerably towards an eastern trough. It retrogrades the ridge rapidly, leaving only a narrow window for cold. But the trend is your friend with this model. What a great look around 276. -The ridge is retrograding for sure. It remains to be seen whether it stops in the EPO region or continues to retrograde into Asia as Holston correctly noted is a risk. I think it sticks the landing, but that is only a hunch. -Mammoth is getting hammered today as is Los Angeles. There may be rain in the Rose Bowl. -Good trends w/ ensembles at 12z. With deterministic runs all over the map...this is probably the best way to go. -Increasing risk of a stalled frontal boundary. The 12z GEM has it at 240, but as Icy would correctly note...it is 240. The 12z Euro flirts with that as well. That risk is even more apparent on ensembles. I don't see a big snow accumulation bump, but one can easily see the gradient pattern s/ a slight southwest to northeast axis after Jan 10. Thats's all. Oregon has already scored while I right this. Ducks up 13-0...the Ducks are pulling the truck!

Less subtle hint...the 12z GEFS ensemble runs looks good as does the EPS. That energy getting held back in the Southwest w/ a trough over the east. Yeppers!

The 12z GEFS has flipped to an eastern trough. Look at it at 18z last night. Look at it now. @Holston_River_Rambler, thanks for the PDO numbers. It looks like it is trending away from severely negative. We just need it to get near neutral so it isn't default Mountain West trough.

As for the MJO, the CPC plots have it all over the place and all over the COD, but with very low amplitude. I can't find a single plot that gains amplitude. It is very difficult to find even a pattern among the cobwebs of plots. I think Jax's chi image from yesterday is pretty accurate. Six is going to fire-up for a few days, and then fade. There will be mild activity in the 8 region continuously. The signal gets washed out. I did think of this. Can anyone post the daily PDO graph (the one with the running line graph so we can see a trend)? I am going to get my run in for this AM and watch some CFB playoffs. I probably won't post about 12z until the last ensemble runs(EPS) around 2:30. I know some of you think when I don't post...it must have been a bad suite. Nope. Life just get in the way as it should! This is going to be a great football day.

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.