Carvers Gap

For really the first time in a few weeks, ensembles are pretty bullish with the exception of the GFS/GEFS which are just worlds apart from any other model - even its own AI model. They are outliers. In my book, though, the deterministic models have led the way. Something is not right w/ wx modeling right now. I maybe can remember one winter where modeling was completely blind to cold fronts. The GEM, with its cold bias, is useful right now, because it exaggerates the pattern enough to find them. Sometimes when graphics are exaggerated (like increasing exposure on a camera), one can spot details which can't be spotted otherwise. In this case, the GEM is spotting cold fronts in a similar manner. Just subtract the cold bias. My guess is the mistakes are occurring with the MJO region which has no real clear signal, the extreme cold in Canada, the NAO stepping onto the scene, and was the Aleutian high over estimated in terms of staying power? Throw in some atmospheric river stuff...and it is understandable that struggles are occurring. But this deal where the GFS can't even see a cold front past d7 is really weird - something has been tweaked in the model IMHO. It is just missing wildly right now...unless the pattern is warm.

The trend of models being blind to cold fronts (until a week out) appears to be continuing. Just so very odd.

I mean the Jan 2 trends are pretty stark. Models don’t have the below zero axis of the cold air mass on the GEM, but they have completely erased positive temp anomalies at that time and shifted SW with the cold towards the Ohio and Tennessee Valley regions.

12z trends are towards the GEM…to be clear not to that extreme, but a cold eastern US.

The 12z ICON has moved to the 0z GEM at 500. Let's see if the 12z GEM actually holds to the 0z GEM!

As for Mammoth...their webcams are awesome. I dropped a link for their cams on the mountain. Just another world for snow rates. The cams range from 8000' to 11000'. We stayed at 9000' this past summer when we were out there. It is crazy to see everything buried now. The ground was bare two days ago - they had almost no snow below 9500'. Very late season for them. (Some Colorado resorts further east still have bare ground.) If they didn't get this storm, I am not sure when they get another window like this. But...it is easy to see how the Donner party got caught. People were hiking up until two days ago in the 10,000' range...today, you would be stuck. I mean the ground in the Sierra Nevada was bare. They have been super warm while the East has been cold. The 6z AIGEFS lent a bit of support to the 0z GEM - it doubled its colder members since 0z. We probably are going to have to look at ensemble members in order to sort the cold fronts out for early January. The mean will continue to be skewed until the last minute I think. https://www.mammothmountain.com/on-the-mountain/mammoth-webcam/woolly-cam

The GFS IMHO continues to be a bit of an outlier as it forms and breaks down the NAO rapidly. I can’t find another model doing that. I can’t remember which model handles the NAO better. Who know? It might be right. The GEM is another adamant outlier outlier with its solution. I would guess it continues to trend towards a NE cold shot vs Deep South. But it has a good habit of finding cold fronts, albeit too intense with its solutions. The Euro looks like good middle ground - for now. I would not be surprised to see models trend colder after a warming trend over night. We have entered that 5-7 day window where things get lost. Also, it would not be surprising if models were simply too quick with the cold. I am noticing a trend to send the cold on Jan 5 instead of 2nd….even the 8th. Models are bouncing between those dates. Remember in late November that modeling had the cold, lost it, and then brought it back. I would not be surprised if we see something similar now. Been kind of a weird year with model biases and feedback. With the exception of the GFS, other modeling has the NAO. So, a great sign that it is still present. I think it is the Euro which eliminates the Aleutian high late in its run. Either way, Merry Christmas to all of you! Have a great day!!!

LOL. That is a great line. I always forget about mountain torque events in Asia. I am assuming this is good or us?

Just looking at the 18z EuroAIFS....that is a pretty good look. It is wild to see the Jan 2 cold front trend today. I think we see several cold fronts forced south and east. That seems like it has slider or clipper potential. But with modeling bouncing around right now.....I hope today is the beginning of the ship being steadied, ie we get a fairly predictable pattern.

I have been wanting to post that GEM map all day. We were doing Christmas with some of my family...I definitely was sneaking a peak at models. But my 12z model deep dive...just now happening. There is an interesting demarcation point after the 5th...does it warm up and we get a heavy rain event as Holston posted? Or does end up frozen(not at those levels)??? I tend to think the cold hangs around, but that is an educated guess and by no means fact.

The very definition as an outlier, but it deserves its moment since it is inside o 240. Departures from normal....That would include -11F IMBY. I have to look at chinook maps for a couple of weeks on modeling. So, humor me...haha.

I have found that the Euro coupled with the GEPS(Canadian ensemble) has been decent this winter. When the two are singing the same song...good thing. When the GFS starts to trend towards them...better thing. The GEM only goes out to 240, so I kind of use the GEPS to see where it might have gone if it went past 300 hours at the deterministic level. Both get to a pretty similar place. BTW, the ensembles have moved quite a lot over the past 48 hours. Right now(rightly or wrongly), I don't trust any model which breaks the NAO down too quickly. Unrelated, it just kind of seems like about the time the NAO makes its exit...the EPO/PNA is gonna pop. That has been a pattern for several winters. NE TN folks have generally not benefitted from this, but with the cold pool so strong...I have to think the cold doesn't get held up at the Plateau or even the Apps.

Some great trends on modeling for the past week or so....still a tough pattern to model. I like @John1122's analog discussion above about 1982. It was one of only two Tenn winters which I missed while living in winter purgatory - Orlando, Florida. I read the newspaper articles about the ice storm, and about Tennessee beating Alabama during the World's Fair. I will say that it got crazy cold during those winters in Orland and wiped out many orange groves that were never replanted.

The 18z GFS find the cold air mass. All...winter...long -> so far. It has almost 50 degree changes(colder) over the GLs. Trending quickly towards what the GEM has had for days. The 18z AIGFS is on board. Honestly, there are so many cold fronts modeled...I have no idea how many there are. Dec 29, Jan 2, Jan 5, Jan 8?.

Now, merge that with the 12z GEM...and we are in business!!!