Carvers Gap

That is insanely good information, John.

Haha. The 18z GFS has freaking hurricane in the Gulf on December 6th. Not sure I have seen that before!

Here is the difference in the control for all of December...Notice what is gone. This also correlates with the MJO looks we have seen. The SER wasn't pumped by multiple Baja lows.

I think that trough is baked in the cake. It should be COLD. Nice animation. How did you get the GIF for WxBell to work?

These are the changes for week 3 of December. Ridge is out of the Aleutians. There is no ridge bellying into the SE. This would allow for northern stream systems and sliders. The control is MUCH colder than this.

Comparing week 2 of December. This is the change which is seen on the Euro Weeklies. This was derived from the 0z run. The 12z derivation would have certainly been even better. Notice the SER is gone. Notice the EPO ridge? It isn't in the Aleutians which teleconnects to AN heights over the SE. That is a 1,000mi change in the Eastern Pac ridge. There are AN heights over Greenland. Those changes IMHO are a direct result of things resolving w/ the erroneous(?) Baja low. The SER doesn't get pumped long term. addendum: Yesterday, the blues and yellows were exactly where u didn't want them. Today, they are generally where you want them

Noticeable shift colder today on most models with the exception of the CMC deterministic. The Euro Weeklies have returned to their cold look and serviceable 500 pattern for December. By the second week of December, they begin to push the cold for the rest of that month - equilibrium restored. The Weeklies, contrary to some comments on other forums, had a major change about two days ago. That first week of December has pretty much been warm on those Weeklies for some time. Nobody is upset about that. The thing that was frustrating to see was the Weeklies completely lost the rest of the month of December, especially after nearly 4-5 weeks of cold being shown. The Euro Weeklies have been anything but steady this past week - welcome to shoulder season. I really think the problem was feed back over the Southwest. Now that is being resolved with each passing run, modeling(deterministic and ensembles) is beginning to correlate again with the MJO and LR ext modeling.

The 12z Euro deterministic also kicks out the energy out of the Southwest. The EPS is a little slower to do so, but I am going to guess it does the same. Both the 12z GEFS and EPS have a formidable cold look now. The SER flexes are short lived. Just file this one away for later used. I would say 75% chance that what we saw yesterday was feedback across all modeling. It caused havoc downstream from that. I would suggest modeling in the d8-14 is still in the process of correcting.

The 12z Euro has correct as well. Storms are kicking out of the Southwest as one would expect. Now that modeling is getting that fixed, we should see some downstream corrections. I would expect for something to track pretty soon.

I think the multiple cutoffs to Baja and/or Southern Cal....was an error. The GFS has a bias to be progressive, but because of that it will work this out more quickly. The 12z gfs and ensemble matched the 6z run. The CMC is still coming around. In fact, the GFS is flirting with snow around Dec7-8. My guess is that cuts along the Ohio River Valley. But things don't hang up...that cold front will come roaring through at the end of the first week of December.

Overnight, it looks like the GFS started to get rid of the feedback over the SW. The 6z run pretty much eliminates it after the 6th. There will be a cutoff out there, but the GFS(and its ensemble) kick out everything after it. Is this because the model has a progressive bias? Maybe. But it would also be the first to fix whatever is going on(if indeed there is a feedback error which seems to be growing more likely).

Hour 276....we have some things to get worked out. The difference in the Euro AIFS and GFS ta 18z over Nashville is 58 degrees. The Real Feel on the AIFS is 3. The GFS is 61. The AIFS did not dig into the SW w/ the SLP FWIW, but it did the second. That still allowed a massive cold front to crash eastward on Dec 3 on the AIFS. The AIFS even dropped 1-3" of snow north of I-40 from Nashville eastward.

Option 1(and there will sure be options 3,4, and 5!) is that the trailer vortex spins out to sea. That is the 18z version. Option 2 is what happened at 12z. The trailing vortex followed and dug out a huge trough which allows a third vortex to drop into. We need that first vortex (even if it goes to the FC...to dig less and kick earlier). I think the first vortex digging into the SW is legit. I am not sure I buy the second and third vortices doing the same - that smacks of feedback. If the second and third vortex simply "don't go to Baja" then the trough likely digs into the EC. Take a minute and looks at the little vortices which modeling is juggling. There are four rotating around the EPO ridge - not counting the Four Corners low. This set-up is an absolute thorn to work out. The downstream effects are huge. It will be interesting to see how this works itself out. OK, enough stream of though posting. It is Friday night, and I am chilling. Will check back later.

Night and day differences when the SW doesn't have multiple lows cutting off...I don't know which is right. But the 18z GFS gives me some hope that the multitude of cutoffs in the SW may well be a feedback error.

The second vortex (which follows the Four Corners low) is the problem. During the 18z run it literally cuts directly through the ridge in the GOA. At 12z, it cuts over the top and dives into Baja which deepens the western trough. You can see the variations on the panels of the ensembles. About half have a trough in the East and half have a ridge - thanks to that little vortex. The EPO ridge is so tall that it is rotating energy back under it which is causing westward flow of Cali. If that vortex doesn't sit over Cali, I do wonder if Santa Anna winds might develop as a result. edit: When the first Four Corners low doesn't dig as much, it doesn't really leave much room for the second to follow. All of this is something to watch on future runs. Until this gets worked out, everything from Weeklies to deterministic runs are going to be impact IMHO. Why? That series of cutoffs takes almost a week to resolve. In other words, there are 5-7 days of cutoffs if not more (on previous runs). If we are looking at just 24-48 hours of a single, cutoff low...that allows for the trough to form in the East. It is a great example of the butterfly effect. The difference between record highs at 12z and the PV heading south at 18z....look nor further than the SW sequence.