Carvers Gap

Glad @John1122reminded us of the basketball game. Wow. Insanely good on offense today. You all know that I like the Euro controls. I went back to the last 7-8 runs. They are alternating almost perfectly from warm to cold...every other day. Well, here is today's, and this has support across the 12z suite(even though this was a 0z run). This is a 30 day map for the month of December. Lot of big troughs swinging through w/ the SER flexing as the cold retreats. To me at least, that seams like a reasonable pattern compromise.

I have repeatedly watched the deterministic GFS lead the way over other deterministic and ensembles at this time of the year(during past winters). It maybe doesn't do that as we get later into winter, but it seems to do a little better(than other models) during late shoulder season and early winter. I do admit ensembles carry more weight, but a lot of those ensemble members are cold. At the very least, some very cold weather is not out of the realm of possibility. And if the trend continues during future runs, those ensembles will flip. Fun 12z suite for sure. Pretty big cold signal for Dec 3 and/or Dec 6.

I don't think that is look is a slam dunk, but nice to see 12z deterministic runs(across the board) show a great pattern. Ensembles are understandably slow to respond. I think a lot of the mean temps are skewed on the ensembles. There are 4-5 big ridges out of 20 members. The temps under those 4-5 members are skewing the mean. If those were tossed as outliers, the mean would be much colder. Hopefully, those warmer ensemble members begin to exit as we get closer...that could mean deterministic models may be closer to being right.

Ah, yeah. Thanks for the reminder. I about forgot about the mid-day game!!!

IMHO, there is a decent storm signal showing up IF the cold settles into the Ohio River Valley. There are multiple CAD signatures for W NC. I would also think there is potential for winter storm across the upper tier of the Upper South with the way that storm track sits. We will see if this trend continues going forward. This started late yesterday with both the AIFS and GFS trending colder. The 12z suite is cold across the board. It could just be a batch of data or it could be a continuing trend.

The 12z Euro bring subzero temps into the Ohio River Valley(western sections) 2x. Once is around Dec 2nd and the other is Dec 6h. There is probably some snow field enhancement there, but still...it is very cold here. Single digit real feels by Dec 6th. Maybe a couple of days w/ sub freezing highs for areas north of I40 on two separate occasions.

The 12z Euro looks remarkably similar to the 12z CMC. I am kind of surprised by that. Winter storm potential exists on it as well.

This is the 5-day map from WxBell of the above pattern depicted by the 12z CMC....that is a BIG change. What we are seeing at 12z might explain the model mayhem. Is it the MJO finally exerting influence on modeling? I have sometimes noticed that the MJO doesn't really exert influence on modeling until about d10-12. I have noticed this in reverse when the pattern looked cold d10-15, but the MJO looked like it might stay cold while in the warm phases - nope, almost always flips as reality approaches. Is the SSW starting to have an early impact on the troposphere? Maybe, but it is a bit early for that influence. Either way, the EPO is showing up on modeling big time at 12z. Let's see if the Euro gets on board. I kind of doubt that it does as it IMHO is dealing with feedback issues in the SW. But let's see if it gets moved off of its spot just a little.

And the 12z CMC has similar look to both the AIFS and GFS. EPO anyone?

The 12z CMC has a below zero air mass sitting in the Plains and Ohio River Valley as a couple of impulses originate in the Gulf and head northeastward.

The 12z CMC almost has a winter storm by 198. Big changes on the deterministic models at 12z today - noted that the Euro has yet to run. The Euro AIFS, GFS, and CMC are showing a cold shot around d10-12 which wasn't there on yesterday's runs. It is a bruiser. I doubt the ensembles will switch that quickly, but it is a trend worth watching. This cold front had been on LR ext modeling for weeks, and then disappeared. edit...the CMC is actually close to something good 3x.

The 12z Euro AIF is rolling. You can send me the Christmas card later (for saying the first week of December being warm was a foregone conclusion). LOL. That right there is not a warm look for the eastern 2/3 of North America.

And this would be phase 8. Now, I must warn everyone(newbies especially) that model talk past d10 is not without peril. But it sure seems like the GFS (and about half of the recent AIFS runs) are sniffing out a potential cold shot around December 6th.

And this is a setup that says, "Look out!" This is sitting at d10. As @Holston_River_Ramblershared yesterday, the AIFS caught wind of this possibility first - I failed to note that early...sorry Holston! The GFS is now picking up on the possibility. That is a mechanism for fiercely cold air to be discharged into the Lower 48, especially the Northern Plains, Ohio River Valley, and maybe the Tenn River Valley. There is the possibility that this is being under done. Either way, this is a very cold look at the surface.

And it is very important to be careful w/ 500 maps with cold air on the prowl. I was watching temp maps that were frigid at the surface, but the 500 map looked benign. The surface map(first image) shows a strong cold outbreak into the Tenn Valley after 300 hours. See that string of high pressures. However, the 500 map looks kind of meh. I think there is a 50/50 chance that we see a strong cold outbreak in/around December 6th.

The 12z GFS now has a true Arctic outbreak at the end of its run which is exactly what we would expect to see with the MJO flirting with phase 8. And I have said this many times, the GFS deterministic would likely be the first to spot something like that. I don't know if it is right, but it fired the first shots yesterday at 18z.

I think the end result of all of this will be some wild swings between cold and warm. The frequency of the troughs and ridges is high. The troughs are deep and the ridges are high. That is a formula for wild swings from model run to model run. I do think troughs tucking under the EPO ridge is probably an error. It is not without precedent, but it usually isn't common this early in the season and especially with an MJO that would want to kick a trough out of the West. The runs which make the most sense are the ones where the troughs get booted if/when they form(from the West). I think the progressive nature of the GFS is probably muting that feedback.

I do believe the GFS is now starting to sense the MJO. That is a MONSTER EPO ridge on that model to begin December. I highly doubt the downstream consequences of that are worked out yet.

If I am cherry picking models...I sure like the 6z AIFS paired w/ the 6z GFS.

The difference between 0z and 6z on the GFS is stark regarding the long range pattern. I think it likely we deal with warm temps through the first week of December, but that is not set in stone as there is a cold front possibly coming through Dec 6th(up in the air so to speak).

Model whiplash....12z CFSv2 and 18z CFSv2.

Bonus post....sorry. This is why the LR is a mess in terms of, "What will it do?" On this map, we have many conflicting signals. We have a second tropical-ish system south of the Yucatan, a low east of Hawaii(good), a PNA ridge(good), a cold front crashing eastward (good), a -NAO (not good), a block and a half over Alaska and the Bering Sea( I can't even remember the Bering Sea rules), a -AO(not good), a GOA low(normally not great), a western Atlantic Ridge (WAR), and cold over the interior of Canada(good). I could make a pretty good case that if the "movie is played forward" that this is has the potential to empty a lot of cold into NA and eventually the EC by the second half of December. Again, if any model is going to sniff out a cold shot at this time of year(December), my money is on the GFS. By my count the 18z GFS has (4) cool or cold fronts which make it to the west side of the Apps. And that is it for a bit...I have been watching things today, and wanted to sit on a few model cycles before posting. Plus, it has been a busy weekend.

The last in a flurry of posts...I do like the GFS at this time of year. By mid-late December, I like the Euro better for medium and long range accuracy. The 18z GFS isn't a bad pattern. Maybe keep an eye on the Dec 6 timeframe. For the past several runs, the GFS really wants to lift something out of the Gulf. I have definitely noted over the years that the GFS will often spot a cold outbreak more quickly on the deterministic d10-15.

For clarification of my above model verification comments. @Terpeastposted this. For future reference, based on MJO verification over the last 30 days, GEFS is really the one to watch when MJO is medium to high amplitude. And it’s not even competitive.

Really there are two BIG things models are trying to navigate. It is going to take some time for them to "get right." 1. SSW - to what extant (if any) does this impact NA or the surface at all??? 2. The cutoffs in the SW. It sure looks like feedback after system one. I have been fooled by modeled cool forecasts for December before. Conversely, I have seen LR extended modeling show cold, reverse course to warm, and then revert back to the original cold look. So, I am gonna just "chill," enjoy the Florida beat down aftermath, and eat some great Thanksgiving food this week. We certainly could see a warm temps in phases 8-1-2. It has happened before, and could happened again. But I have also seen deterministic modeling flip very cold once they recognize the MJO phases - almost all at once.