December 2020 Medium/Long Term Pattern Discussion.

[Holston_River_Rambler]

Here's the 500 mb pattern @Carvers Gap was talking about:

 

 

 

[nrgjeff]

Monday morning a little wave digs in for the Upper Plateau and perhaps northeast Tenn. Only relevant at elevation. It's post-frontal so Sunday night clouds are not a huge factor. Still the boundary layer will be too warm in the Valley Monday. Curious to see if anyone documents anything Monday.

Unfortunately I have nothing positive to say about days 3-15. I'll go with, if I don't have anything nice to say I won't say anything at all. Good luck Monday!

[Daniel Boone]

11 minutes ago, Carvers Gap said:

The 12z EPS AO is at -2 in places.  So, looks like if we are going to have winter...the Atlantic is the ticket(think Jeff said as much in the winter thread).  The MJO continues to look putrid which is a surprise to me.  Would not be surprised to see it rotate over to 7, 8, 1 in a couple of weeks as some of the OLR maps show a diminishing wave over the warmer phase areas in the wester PAC and Indonesia. 

I'll say one thing, you can bet the monthlies will bust big time if that high latitude depiction is realized throughout the Winter at any sustainability.  Those Monthly runs put alot of weight in ENSO .

[Carvers Gap]

12 minutes ago, Daniel Boone said:

I'll say one thing, you can bet the monthlies will bust big time if that high latitude depiction is realized throughout the Winter at any sustainability.  Those Monthly runs put alot of weight in ENSO .

The Atlantic is the wild card in modeling right now.  Will it actually verify?  Still think the warm water in the NW PAC makes it tough to put a trough into the West without a ridge popping there from time to time.  Good trends in the LR compared to two days ago - not great but not terrible.  Thing is those -NAO looks seem to be a bias and/or also seem to pop right around the time the SPV gets jostled.  Definitely not bailing out on winter on December 6th.  Probably going to be long bouts of warm, but have to think we see some shots of cold from time to time.  If anything this year has taught me, take it a day at a time and enjoy each moment....well and 2020 has certainly proven that things can change quickly.  

[Daniel Boone]

Will add, looking at the last evolution of the esp run. It does go zonal even with the blocking. That AK Vort is suppressing the Niña forced Ridge but instead of it shifting east or west, it just flattens and thereby causes a screaming Pac Jet. Not good. So. I may eat my above words.

     Would be nice if that AK Vort would continue west and set-up along the Aleutians. 

[Carvers Gap]

1 minute ago, Daniel Boone said:

Will add, looking at the last evolution of the esp run. It does go zonal even with the blocking. That AK Vort is suppressing the Niña forced Ridge but instead of it shifting east or west, it just flattens and thereby causes a screaming Pac Jet. Not good. So. I may eat my above words.

     Would be nice if that AK Vort would continue west and set-up along the Aleutians. 

Nah, it is LR forecasting...we all eat our words often!  Great thing about our forum is we can throw ideas out there and take chances.  Only way to get better is not to be afraid to be wrong, right?  Definitely has a zonal look.  One thing I have noted is that the LR models have missed strong trough amplifications of late.  Anywhere where trends are heading BN may well be much colder as time gets closer.

[PowellVolz]

I haven’t kept up much with mods the last few days but are we not liking the 14-17th much anymore?


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[Carvers Gap]

MRX afternoon disco...

https://forecast.weather.gov/product.php?site=MRX&issuedby=MRX&product=AFD&format=CI&version=1&glossary=1

Soundings show rain changing to snow across the highest peaks of
our mountains shortly after 06Z tonight. A good burst of snow is
expected from 09Z to 12Z as lift is maximized due to strong
vorticity moving through with the trough axis. 1 to 2 inches are
expected during this time. From 09z to 12Z is also when valley
areas have the best chances to see some rain, and perhaps a few
snow flakes where cold enough.

After the trough passes, around 12Z, the winds shift to the
northwest and the mid-levels begin to dry out. When the wind shift
occurs is when the northwest flow snow machine takes over across the
eastern mountains. The favored upslope areas will see snow from
12Z Monday through early Tuesday morning. The bulk of the
accumulating northwest flow snow occurs between 12Z Monday and
21Z Monday afternoon, then tapering off to lighter snow showers
through early Tuesday morning. Total event snow, 06Z Monday
through 00Z Tuesday is on the order of 1 to 3 inches above 2500
feet and 2 to 4 inches above 4000 feet. Locally higher snowfall
amounts are possible across the highest peaks.

Elevations below 2500 could see minor accumulations from a
dusting up to half an inch near the foothills of the eastern
mountains and across portions of southwest VA. The northern
Cumberland Plateau may see a dusting. A winter weather advisory
will be in place from Midnight tonight through Midnight Monday EST
for portions of the east TN Mountains. A few flurries will remain
through Tuesday morning.

For Valley locations, flurries may linger after day break across the
central valley and northward but will taper off through early
afternoon. Clouds will be around for most of the day with temps only
climbing to around 40 degrees and breezy northwest winds will make
it feel even colder with wind chills around freezing. Wind chills
across the highest elevations will approach single digits from late
Monday afternoon and through the overnight hours.

 

[Daniel Boone]

1 minute ago, Carvers Gap said:

Nah, it is LR forecasting...we all eat our words often!  Great thing about our forum is we can throw ideas out there and take chances.  Only way to get better is not to be afraid to be wrong, right?  Definitely has a zonal look.  One thing I have noted is that the LR models have missed strong trough amplifications of late.  Anywhere where trends are heading BN may well be much colder as time gets closer.

Thanks for the uplifting comments buddy. That warm pool you mentioned may help pump a ridge there as you mentioned from time to time and mitigate that zonal depiction. That could work for us and maybe, I won't eat those words, lol.

[Carvers Gap]

1 minute ago, PowellVolz said:

I haven’t kept up much with mods the last few days but are we not liking the 14-17th much anymore?


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Cold shot comes through the 13th.  Right now looks dry before the next system may cut right at the end of that timeframe you mentioned.  IMHO, still a lot of uncertainty during that time frame.  The 12z Euro operational has a really strong trough amplification then.  Would not surprise me to see something along the EC.  Euro pops a low off NC around the 15th.

[jaxjagman]

Nice trough going through East Asia which is being modeled around next Sunday which should effect us around the 21st give or take.Problem it seems lies within the teleconnections,fairly substantial spit within the NAO/AO

[jaxjagman]

Have to wait and see what teleconnections have in store,but right now this seems more severe than winter

[Holston_River_Rambler]

Yeah that would be ugly. Solstice severe on the control after some ice. Double the Christmas power outages = double the fun. 

[John1122]

Probably the most positive about that EPS/GEPS/GEFS long range, a crap ton of cold should build across Siberia, Alaska and Canada as we approach the first day of solar winter.  Those regions are ultimately our source for cold air when it gets tapped. The pattern looks changeable enough that we could get some very cold blasts during relaxations in the warmth. Those are fairly common in La Nina patterns historically, though I pause to use historical outlooks these days because they don't seem to work out as often.

[Carvers Gap]

2 hours ago, jaxjagman said:

Nice trough going through East Asia which is being modeled around next Sunday which should effect us around the 21st give or take.Problem it seems lies within the teleconnections,fairly substantial spit within the NAO/AO

Hey, man.  Glad to see back posting more.  

[Carvers Gap]

4 minutes ago, John1122 said:

Probably the most positive about that EPS/GEPS/GEFS long range, a crap ton of cold should build across Siberia, Alaska and Canada as we approach the first day of solar winter.  Those regions are ultimately our source for cold air when it gets tapped. The pattern looks changeable enough that we could get some very cold blasts during relaxations in the warmth. Those are fairly common in La Nina patterns historically, though I pause to use historical outlooks these days because they don't seem to work out as often.

That is kind of my thinking.  Maybe get some truly cold air into the Rockies and let it bleed eastward at times.

[Carvers Gap]

DT is mentioning a fairly significant weakening of the La Nina (maybe in the Euro sesaononals) over the next six months.  Not sure that helps us at this latitude as it might not help until March.  That said, I will take a weakening Nina vs a strengthening one.  It is very important to note that most ensembles, monthly model runs, and seasonal models missed the December cold snap.  I will post the Euro seasonal for December if I get a chance later.  That said, if the Euro is going to miss...Nov/Dec are usually excellent candidates.  

[Carvers Gap]

Also in the "evening" news from the MA forum(above info was from there as well), the 18z GFS does put the hammer on the SPV.  Bout all I got for now.

[Carvers Gap]

About 300, the 18z GEFS has a ridge now out West.  Likely temporary, but illustrates the uncertainty after the 18th.

[BNAwx]

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!

 

[jaxjagman]

7 hours ago, Carvers Gap said:

Hey, man.  Glad to see back posting more.  

Thanks,it's been a rough time with my wife having cancer.Everything is going ok right now tho ,no set backs or stuff like that

[Holston_River_Rambler]

Strat still looking interesting this AM, as a follow up to what Carver's posted last night. This is not meant as any sort of critique of his post or the post in the MA forum, but the 500mb ensembles still look similar to yesterday, so I thought I'd go strat. hunting. Although IMO we're still too far out to know what if anything is going to happen,  I do  think there will be an attempt at a warming or split in the next 10 - 15 days. Whether it meets the criteria for a SSW or produces anything in any way useful for us, remains to be seen. 

Looks like it is kind of a mixture between a bottom up and top down event. 

50mb on the 0z Euro:

 

There's stretching and some splitting at this level and the 0z GFS shows what the Euro could show if it ran past 240 hours:

 

A weakened vortex tries to reconsolidate, at least at this level of the atmosphere. 

 

Higher up, the Euro sees the warmth building over NE Siberia, but no split:

 

GFS gets the split at 10 mb, but also reconsolidates:

3D vortex page is usually a day behind in the GFS runs, so I can't show it in that format. 

 

I'd like to see it within 3 - 5 days with some ensemble agreement to start really thinking about if a SSW or split is going to happen or not. 

Still looks stout on some ensembles, at least at 10 mb:

At least it's are looking weaker than last year, lol:

 

And as a lesson from last year, here is how a similar, almost split, could reconsolidate:

Last year's SPV was a record strong, so not sure it will be that way again. But it is still 2020...

I had my year off from SSW and splits last year. I'm good to go for another one, as long as it doesn't wait until Feb, to make a miserable Spring. 

 

 

 

[Holston_River_Rambler]

I will say the overnight OP CMC and Euro look interesting towards the end of their runs, but it is in that seemingly-always-present, but-seemingly-never-quite-realized, 8 - 10 day period.

Both show a wave trying to ride a front after it passes through. CMC on Dec 14 and Euro on Dec 17. 

[Carvers Gap]

I have to be honest...I am not seeing a locked-in pattern on the operational runs at all.  Just looks like a pattern with a lot of variability.

[Carvers Gap]

Whew.  Good luck making heads or tails out of any of those runs - GEM or GFS at 12z.  Lots of cutters.  Maybe one or two taking the low road with cold air lacking.  When models goes haywire like that, makes me wonder if we are about to see some very cold air invaded the lower 48, maybe just after the day14-16 window(basically just outside of modeling's range).   Lots of chaos in those two model runs.

 

[nrgjeff]

I see the PV bending but not breaking. Then it tightens up again in an act of defiance. Pretty dismal forecast tbh. When's the next chance of severe weather?

[Carvers Gap]

12z Euro continues with a progressive pattern of cutters and low road lows(which lack cold).  What is actually cool about that run is that it has the AK to SE trough(albeit temporary) which ensembles have struggled with for about a week.  Some bitterly cold air in north/central Canada along the eastern shores of Hudson Bay.   

[Carvers Gap]

I personally didn't think the Euro Weeklies looked terrible for 850temps(I never uses its surface temps...terrible warm bias) and 500 maps.  The 12z EPS was quite a bit different.  In the past few runs it has eliminated the ridging under neath and was quite close to opening the door for the air mass in AK to drop into the nation's mid-section.  Will try to post more later.

[Carvers Gap]

The Weeklies seem to imply that the cold is going to push after initially going West.  And that is extremely cold air in Alaska.  When operationals start to bounce around usually some very cold air in NA...noticed both of those characteristics at 12z today.

[nrgjeff]

Agree the next 2-4 weeks will have cold fronts and wx systems. Weeklies show a trough in the GoA but significant Greenland ridging. That's not stable SER material, though I agree the volatility probably averages out mild. 

Weeks 5-6 lose the blocking; and, go with a more stable SER situation. However weeks 5-6 are subject are subject to dispute.