December 2020 Medium/Long Term Pattern Discussion.

[Carvers Gap]

On 12/6/2020 at 7:20 PM, BNAwx said:

As long as we can hold on to the warmer waters in the NE Pacific, I think we’ll be ok.  That should give us intermittent opportunities for some cold to be dislodged whenever the PNA decides to spike.  If we can hold any Atlantic blocking and slide the ridging into the EPO region, we could be looking at some brutal cold heading our way.  I could be way wrong but I don’t see the PV being locked in an unfavorable position for the entire winter like the last couple.  I’m also liking the MJO forecasts.  It doesn’t seem to want to stray into the warm phases (and strongly at that).  I certainly don’t think that’s a bad thing depending on other factors.
 
I would’ve really liked to see the subtropical jet continue but being a Nina, I guess that was too much to hope for.   However, it’s winter in the South and all it takes is the slot machine to line up just once and it can make it a memorable winter.

Anyway, I follow you guys often, especially this time of year.  Not much time to post anything of merit.  Great analysis by all and I hope we as an entire forum can have something noteworthy happen this winter!

 

BNA, I missed this post earlier in the week.  Yeah, pretty interesting to see the impressive blocking over Greenland on overnight ensembles and maybe winter storm potential as well.   

[Holston_River_Rambler]

It's wild @TellicoWx Even most GEFS members don't have much, though some have the wave. I can't tell if the new GEFS is more favorable than the old one (still available on COD:

6z Old GEFS:

 

 

New GEFS:

[Carvers Gap]

2 minutes ago, TellicoWx said:

GFS/Euro usually are at odds with each other but this is par for 2020 I guess lol...6z GFS=Noah's Ark across the Mid south/TN valley..0z Euro= Winter wonderland..polar opposites

They are for sure.  Tellico, (and I haven't looked at the GFS closely) does the GFS look too progressive and have confluence too far to the East?  Which model handled the last system(where it snowed) the best?  

[Carvers Gap]

Just now, Holston_River_Rambler said:

It's wild @TellicoWx Even most GEFS members don't have much, though some have the wave. I can't tell if the new GEFS is more favorable than the old one (still available on COD:

6z Old GEFS:

 

 

New GEFS:

These days, the ensembles don't differ as much from the operational runs like they used to, IMO anyway.  I think if we take the progressive nature of the GFS and the tendency to slightly overman by the Euro...there is a window now for a storm.  Guessing models are having to sift through the various pieces of energy for the pattern.  It does seem like confluence (at times) is over the lower MA next week.  

Have you seen the block on ensembles this morning?  I never really buy that look (burned too many times), but it is getting kind of hard to ignore as it is probably being felt now in the mid-range by storms.  Generally speaking, that block may well force phasing(more often than normal) of systems which are timed correctly.

Anyway, modeling had a really stormy pattern about a week ago and then backed off.  Looks to me like it is coming back to that potential, albeit a few days later than originally modeled.  

[Holston_River_Rambler]

Sometimes @Carvers Gap, regarding the model changes over the past week, I really do wonder how much it has to do with how they initialize tropical convection:

Last week over the MC:

 

This AM:

 

a lot of the MC convection. is south of the equator. although there is more over the Indian Ocean 

[John1122]

Not saying the Euro is going to verify, but events like that do happen here, it's just been a while. One of these days it's eventually going to happen again.

[tnweathernut]

Great discussion, guys!  I have been super busy, but have really enjoyed following along when time permits.  John, I agree, events like this will eventually happen again.

Sure looks like old biases may be at play looking at the GFS vs. the EURO from last night.  GFS is very progressive at 500 (the surface reflects this too).  Just wants to blast everything through the TN Valley and be done with it. 

The Euro tends to overly amp in the long range, but this seems to be sprouting much closer in time, so does that bias really apply here?  Genesis of the trailing frontal (northwest gulf) low in response to the energy at 500 begins shortly after hour 100 (not exactly way out in time).

I think this will be a fascinating early season model dual between the new and improved GFS, and the once almighty Euro (snow vs. no snow outcome aside).  

If the brief west coast ridging can hold on just a bit longer, it should give the energy at 500 more of a chance to dig toward the gulf coast (like the euro at 0z) and develop a southeast storm system.  If the Pacific blasts in and collapses the ridging we probably see something closer to the progressive look on the GFS.  Fairly minor differences at 500mb (18,000 feet up) between the GFS and Euro, but major differences at the surface where we live.

As an aside, I am loving the looks of higher pressures in the NAO region.  Feels a bit like finding a unicorn December through the end of February these days.......

[Wurbus]

12z GFS was about the same through 132 as the 00z and 06z. On to the CMC and Euro. Will be interesting to see which model caves first.

[Holston_River_Rambler]

CMC looks like a compromise favoring the GFS. Still some precip, but the energy is not nearly as wound up.

 

 

 

[tnweathernut]

1 minute ago, Holston_River_Rambler said:

CMC looks like a compromise favoring the GFS. Still some precip, but the energy is not nearly as wound up.

 

 

I noticed that too. A compromise solution at 500 wouldn't surprise me.  The only problem with a compromise would be knowing the surface reflection would be poo poo.  

[tnweathernut]

Regarding the potential early week system............  all hail the GFS?  Maybe it will win this battle, but not the war (later in the week)?

[Carvers Gap]

Well, I hope the GEFS is right in the long term.  The trough retrogrades across northern Canada, through Alaska, and parks itself over the Aleutains...basically reverts into the same pattern that we just left.  This time it would be later December and not early December.  No idea if correct, but a nice look right after Dec 20th(no, I am not gonna say IT).  

[John1122]

The difference in the 00z Euro vs the 12z is the PNA ridging. At 00z is was stronger and it shunted the system further south, that let it wind up more. 12z the ridge was less sharp and the system stayed weak and open as it rolled across the south. I wouldn't sleep on it yet. It may not be a block buster but I wouldn't rule out snow for someone in the region from it.

[Carvers Gap]

Just looking at today's MJO...some changes there.  Looks like the IO is about to go really quiet if the OLR maps on the CPC are correct.  Wave propagates from the MC to phases 7-8 just west of the dateline which should correlate to MJO phases 7-8.  7 is colder the further that one goes into December.  That might explain some of the changes on LR maps at this point.  I think right now with some bitterly cold air moving into Canada, models are going to be hopping all over the place - just wrecks havoc on pretty much all modeling.

[Carvers Gap]

So, I am going to throw this out there.  I think there is a crap TON of uncertainty right now in the LR with possible splits of the SPV, -NAO, etc.  EPS is showing a low getting hung up in the Four Corners in the LR.  Sometimes that is a hint that the trough goes out West.  Sometimes that is a false look and the trough comes East(more likely than not it comes East) - but not a given.  However, with the big -NAO, the MJO looking like it may go into 7(HI RES GFS reference and EMON) at some amplitude....I think we are seeing the signal for a fairly strong EC storm beginning next week and for 2-3 weeks thereafter.  The GEFS is the best look with a classic winter storm set-up.  Going to depend on how much of a SER can nose underneath.  I have been doing this a long time and am certainly fallible on most days, but if that vortex were to slip into the Aleutians with a block over Greenland...the PNA/EPO could pop, amplify a trough, and have the ensuing energy hit the Atlantic block.  That isn't rocket science for winter storms, but the potential is there.  I think the reason we see modeling going with big storms and losing them is that the potential is there.  However, as a friend notes, the PAC is just blasting system after system into that Atlantic block.  Nearly impossible to get timing right outside of 4-5 days.  Interestingly, the GEFS which has never had the storm on M-T next week does have a weak surface low in the Piedmont.  Probably a good time to look at ensemble low placements.  Also, I am thinking some bitterly cold air is a high percentage bet at this time for NA during the next 2-3 weeks.  Would not surprise me to see it drop into the northern Rockies or Plains and slide eastward.  When BN height show up during the heart of winter in Canada, that is some COLD air.

[Carvers Gap]

The CFSv2 has gone bonkers at 12z.  Now, admittedly, it has never seen a cold pattern that it didn't like.  But that is a very cold pattern through the end of its run on the Jan 23rd.  No, I would never share a foxhole with this model, but wow.  Most of NA is cold by the end of that run - NA just progressively gets colder.

[Carvers Gap]

For kicks and giggles, the NAO on the EPS control run - always a red flag(but in this case, really red).

[iluvsnow]

And how about a cherry on top with a possible polar vortex split with the main lobe taking up camp over Canada?

nd the Euro at 50 MB shows a vortex split with primary to North America....

[Carvers Gap]

Somebody remind what this does to the stratosphere and wx in general.  Warm, right?  Either way, very cool graphic...I mean really cool.

 

 

[John1122]

44 minutes ago, Carvers Gap said:

Somebody remind what this does to the stratosphere and wx in general.  Warm, right?  Either way, very cool graphic...I mean really cool.

 

There's some school of thought that solar flares tighten the polar vortex and cause the NAO to go + but that it runs in 100 year cycles that cause it to go negative. You can probably guess which cycle we appear to be in right now. However, not all is lost, just late year researchers at Columbia University in the Earth Observatory and School of Engineering released a paper that pretty much debunked any connection between the two.

[Wurbus]

A long way to go, but it appears GFS is the new Dr. No. Now that I think about it, this totally makes sense in the year 2020.

[John1122]

Starting at 102 the GEFS has most members showing a 24 hour winter event evolving across the Valley.

 

[Holston_River_Rambler]

I kinda feel like, anemic as happy hour GFS OP was, that was the best look it has had so far:

(Using COD for maximal snowage) 

[John1122]

Definitely and uptick in snow across most members vs 12z.

 

 

[Holston_River_Rambler]

The 18z RGEM looks more 0z Euroish now:

 

 

Yeah it's a meso model at the end of its run, but hey, it's happy hour. 

[Holston_River_Rambler]

Here is our disturbance, about to swing ashore in BC. Looks healthy. We'll see if the Rockies are kind to it:

 

[Holston_River_Rambler]

I've seen fantasy Greenland blocks before, but don't think I've ever abv. normal heights over Greenland one for almost an entire run. 

[John1122]

The AO is supposed to go epic in it's negativity.  If the Pacific can marginally cooperate we should be heading for frigid weather later in the month. 

[Carvers Gap]

39 minutes ago, John1122 said:

The AO is supposed to go epic in it's negativity.  If the Pacific can marginally cooperate we should be heading for frigid weather later in the month. 

I am with you.  Throw in a -NAO, and that would be a double block with Siberia being record cold. 

[Carvers Gap]

3 hours ago, Holston_River_Rambler said:

I've seen fantasy Greenland blocks before, but don't think I've ever abv. normal heights over Greenland one for almost an entire run. 

I have seen those the past couple of years - rarely verify.  However, they are often a sign of a SPV.  If we can trap the TPV on this side of the planet(and I think we have a chance), might be fun.