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.