Carvers Gap

The 18z GFS appears to have lost most of its feedback with BN heights coming over the pole at to crash into the eastern ridge. The NAO bout to be tested this run. Let’s see where it goes. Just looking for consistent trends at this point and not random solutions. -only minor feedback on the West Coast this run. So far... -at 300, that is a big time trough in bound...and a monster NAO -Shortly after...the chinook pattern is gone. - Basically, the Chinook has from Dec 24-29th to do its work. It might be the most overtracked feature across forums in many years. Turns out, this may well just be your standard warm-up after a cold spell. -the mechanism is n place late in the run for a full latitude trough w/ trough wedged between an west Alaskan block and a Greenland block.

GaWx has a nice run-to-run post about the 12z GEFS and how it started to lower heights over the NE in response to the NAO. I have had the NAO wreck my ideas more than once(good and bad) both when it appeared suddenly or didn't appear as forecast. It is a true wrecking ball. Until models sort it out, proceeding with caution is wise. I agree.

The GFS and the GEM (if one extrapolates past 240) continue to tease some big changes just after d10. The NAO is trying to be a player. It backs up the entire flow upstream and basically resets the 500 chinook pattern. Is it right? IDK. If we can get a storm to hit the West Coast near Los Angeles, that might do the trick in flipping the trough back East.

12z suite is rolling. I am going to put my thoughts on this suite in this single post. I will simply update it by editing. Feel free to comment. Just know this post is going to have several comments. So, you might "like" one thing, and it might be followed by something you don't like. Haha. 12z GFS -The GFS is really the first model to correct the Pacific NW. It has beens slowly doing this very several runs. Let's see where this run goes. I generally just toss the run if a slp wonders from British Columbia to 500 east of LA. 6z had a realistic solution. -@ 132 the GFS is flirting w/ a winter event over SE KY, SW VA, and NE TN. Probably is WAA, but tough to tell. Interesting development which I don't think has been there before. -The interesting thing is that there is a hp sitting over the top of that. -@ 195 that looks like more feedback over the Pac NW. Interestingly, there is an EPO ridge forming(temporary?). Definitely seems like this timeframe is a demarcation between a good path back to winter weather and on that is not. -@204 that storm off the coast of Cali looks like it might move inland. Any storm that enters at the latitude of Los Angels has to be watched on the EC. Many times a storm will enter and exit at similar latitudes of NA...not matter how far north our south they wonder while over the continent. -@240 generally I just look at the long wave pattern as details are going to change by the next run. The GFS got lost around 195...and ended up with a much different solution -the Dec 22nd cold front is present w/ wintry precip on its northern edge as it departs...big take away and we'll see if it sticks. -I should add that the -NAO is present on this run, but slightly less strong. The NAO is very difficult for models at range, but can make big difference upstream if they form a block. -As wild as that run got, it pretty much got to the same point that 6z did by 270. -300+ The GFS puts the trough back in the East(temporary?). The run-to-run change graphics for this time frame are gonna be fun - really fun. -On both the GEM and GFS...the NAO is east based but having a major effect on the 500 upstream pattern of all of North America. Right now, the GFS has a window from Dec 23-Dec30 for the chinook. Then, recent deterministic runs tend to slam the door on that by the New Year. The real fun begins is if the 6z GFS run blends w/ the 12z run at some point....chinook muted and then trough into the East. Don't know if that can happen, but w/ the MJO in the COD, the SSW may be taking the driver's seat. The NAO would likely be a result of that. 12z AIFS -Looks remarkably similar to the GFS. Looks like around 300 it wants to send a decently amplified trough eastward. Not sure if that is temporary or not, but w/ the NAO sitting up top...that teleconnects to an eastern trough more times than not with the usual caveats mentioned by Boone and me in early posts.

Kind of wild in the wx model world at 0z and 6z. The 6z GFS cuts into the Chinook lifespan fairs significantly. IF the NAO is a realistic player, it is likely going to turn the pattern after 240 upside-down. It sure did last night on several runs.

The 18z AIFS has a -EPO ridge at the end of its run. A lot of this looks like SSW signals - hints of HL blocking.

I think what we will see is the MJO slide into phase 6 as the NAO fires. The mid continental ridge will hook into it briefly. That will create a significant SSW. The MJO will slide into 7-8 as the CHI charts showed over the weekend. The entire cold air mass gets released into a full latitude trough over the US w/ the storm track south of the Ohio River Valley. Good sign if it holds. The NAO will work against us at first, but as it matures...that is when it pays off.

Wow. If that NAO is real on the 18z GFS, it very well could force split flow...and you kind of see it at the end of this run. That will completely upend modeling over the next few days if legit. That would be a major player. The 12z AIFS and 18z GFS now have this.

By 200, the NAO is having significant effects on the run compared to previous runs. The 12z AIFS scores a coup if it nailed it first.

That is a big time NAO on the 18z GFS run. It doesn't have a lot of impact yet, and its staying power is TBD. It may be a forced NAO which just results due to dynamics and is passing through, or it might be the SSW finally working its magic along w/ the QBO. It could hook into the mid-continent ridge, but that generally would cause an NAO and subsequent cold outbreak about 3 weeks later...and has been a common feature of winters of late.

Yeah, cold and viruses have been making laps in my crew. Pretty miserable stuff and hangs on forever as @Daniel Boonenoted. Hopefully the 12z Euro Weeklies are right and we see cold return right after mid-January. The 12z CFSv2 breaks for cold at about the same time. It looks like when the NAO fires(if it fires), that puts a clock on the chinook. Maybe if that NAO can fire earlier, we can return to a colder pattern more quickly. But really, I am good with a couple of weeks of warm weather. Something makes me think the dam is gonna bust at some point sooner than later. One good cutter, and it could all come south.

The 12z AIFS pushes back pretty heavily on the chinook - even more so than the 6z GFS. Take one look at the 500 map, and it doesn't look great. But take a look at what is creeping into Greenland. That is a game changer if it stands(and doesn't connect to a WAR). But take a look at the surface. Not what you would expect. That isn't warm. Cold air is seeping into the EC. A cold hp over the GL is not a bad thing for us. FWIW, the 12z GFS looked ready to break the chinook look by the end of its run. The NAO firing will force everything south.

I will say one thing. The flu is gaining strength in some areas. The blessing of any warmup would be to get people outside some, and get some air. Flu and cold outbreaks go hand-in-hand. I don't think the flu shot has been working super well this season. I will take a chinook over a house full of kids with the flu!!!!!

This is kind of what I am talking about. Two cold fronts are now firmly present right in the middle of the Chinook. Originally, it was torch city. I wouldn't be surprised if some didn't see a snow shower or flurry from this. The 12z GFS won't be as cool as the 6z as it gets bogged down(guess where?) just after 200.

One thing to watch is how wx modeling responds to potential negatives from the NAO/AO couplet. I highly doubt those details are worked out. Now, an NAO during mid-December is pretty meh in my book, but later in December...it could help. Evidently, I cropped the model information from some of these. The first is the GFS 6z AO plot. The second is the NAO for the 6z GFS. The third is the 0z EPS for the WPO. The fourth is the EPS 0z NAO. The fifth is the AO for the 0z EPS. Those are not bad teleconnections for us. Let's see how modeling builds those into their looks for the medium and LR.