Winter 2021/22 December Thread

[Carvers Gap]

7 minutes ago, Holston_River_Rambler said:

Yeah, but it ain't the prettiest control run, lol. I don't have the H5 anomalies for the control, but the 300mb winds give a good idea of the pattern. 

Thanks!  Looks like an EPO ridge creeping towards the WC.  That is the same general look as other models, but a bit slower in its evolution which doesn't surprise me given the Euro's tendencies.  The breakdown of ridge pattern over the East(even if just temporarily) is what I am looking for evidence of.

[Carvers Gap]

Pretty impressive run by the 12z GFS unfolding after d9.  Long way out there, but that is 17-18 level EPO stuff there if memory serves me correctly.  Late December in mid-January.  Super dry but incredibly cold with single digits for nearly a week straight for lows with no snow on the ground.  Not that cold so far on the run...just looking at the direct path from the Arctic southward.

[Carvers Gap]

Cosgrove noted in a post about a week ago to keep an eye on GOA lows.  If they ever move southwest into the Pacific, it sets the stage for the EPO to pop and allow cold air to rush into the Lower 48.  That is what is happening in this run.

[Carvers Gap]

Impressive Alaskan block setting up shop right before Christmas on the 12z GFS run.

[Daniel Boone]

18 minutes ago, Carvers Gap said:

Cosgrove noted in a post about a week ago to keep an eye on GOA lows.  If they ever move southwest into the Pacific, it sets the stage for the EPO to pop and allow cold air to rush into the Lower 48.  That is what is happening in this run.

Yeah, that's what we were hoping strong hlb would do when it set up last month but, it never built into the AO domain. Hopefully, that will be the case and will help force the goa lp sw or even west.

[Holston_River_Rambler]

Euro looked kinda interesting at 500mb in the eastern US at the end of its run.  Not sure it’s worth an gif at 240 hours but I guess the control could be fun past 240. 

[Carvers Gap]

Post 1:  My takeaway from the 12z run is the Pacific (the irony, right?) actually is the driver for colder weather on this run.  No idea if true.  The Euro at 0z was slower with the MJO and the pattern was slower...but with a similar progression.  The GFS is faster in getting the MJO in winter phases, and it shows on this run.  I don't have a preference in terms of accuracy at this point.  I do have a preference in terms of winter wx!!!   

Forgot to post the above...so will just post both posts in this one.

Post 2:  Well, the Euro doubles down on a double block with the NAO strong negative.  Looks remarkably like the CMC.  Now, I think what modeling are seeing are increasing chances for cold in the East during the last ten days of the month, and possibly into early January if we are luck.  Almost all modeling returns to the western trough after that though.  Then I would guess that we see another week or two of warm weather followed by another loading of cold which surges eastward.  That kind of looks like the pattern for winter and looks remarkably similar to last winter.  Good pattern for those in the western 2/3 of the state if that is indeed the pattern.

Fun thing to watch.  If that NAO forms, I am seeing a low get forced into the NAO block.  It slows that low just north of Nova Scotia.  That is a recipe for a big storm as it would suppress the flow and force a storm to climb the coast slowly and then stall.  Maybe a 50/50 low?  Timing appears to be off right now with so few systems in the pattern, but if one were to get in the pattern....look out.

[Carvers Gap]

1 minute ago, Holston_River_Rambler said:

Euro looked kinda interesting at 500mb in the eastern US at the end of its run.  Not sure it’s worth an gif at 240 hours but I guess the control could be fun past 240. 

Posted about the same time you did.  Probably isn't right at that range, but that is absolutely how you draw it up.

[Carvers Gap]

To clarify...how you draw up a major EC storm.  Again, that probably isn't right but that 50/50 has been showing up on multiple runs of multiple models.  Just need timing for something to come along behind it with enough spacing.  

[Carvers Gap]

When is the last time we looked at 12z suite and are like, "Wow, the Euro looked better than the GFS?"  Been a couple of weeks, but that is a great looking pattern.  Ridge off the west coast popping an albeit likely temporary PNA ridge which sharpens the downstream trough.  Then a 50/50ish low is parked in the right spot with energy in the southern jet timed with the northern stream.  Lovely look, but ain't no way that is locked in at that range.  The great thing even though that is unlikely?  The pattern isn't benign.  

[Mr. Kevin]

1 hour ago, Carvers Gap said:

When is the last time we looked at 12z suite and are like, "Wow, the Euro looked better than the GFS?"  Been a couple of weeks, but that is a great looking pattern.  Ridge off the west coast popping an albeit likely temporary PNA ridge which sharpens the downstream trough.  Then a 50/50ish low is parked in the right spot with energy in the southern jet timed with the northern stream.  Lovely look, but ain't no way that is locked in at that range.  The great thing even though that is unlikely?  The pattern isn't benign.  

The euro and gfs so far have a winter event to our west but obviously its early. Sw energy with -pna running into the se ridge with usually leads to ice/sleet providing its cold enough. At least from experience. Stalled front overrunning. 

[Carvers Gap]

1 hour ago, Mr. Kevin said:

The euro and gfs so far have a winter event to our west but obviously its early. Sw energy with -pna running into the se ridge with usually leads to ice/sleet providing its cold enough. At least from experience. Stalled front overrunning. 

Yeah, very different circumstance to get you snow vs MBY in many cases.  The EPS now has the pre-Christmas trough.  That is a legit window now I think.  PNA spikes positive temporarily for that model on the Euro.  We don't need weeks on end of a great pattern, just need a window where it can occur.  Today is the first I have seen ensembles move off their spots.   Operationals are so different, that something had to give.  I generally don't expect snow around my neck of the woods until January or February.  We can get it earlier as we have had two great pre-Christmas snows(after going decades without those), but the norm is a six week window from Jan 1 to the middle of February.  So anything right now is a bonus.    If that 50/50 low is legit, that is important for the eastern half of the forum area.  

[Mr. Kevin]

15 minutes ago, Carvers Gap said:

Yeah, very different circumstance to get you snow vs MBY in many cases.  The EPS now has the pre-Christmas trough.  That is a legit window now I think.  PNA spikes positive temporarily for that model on the Euro.  We don't need weeks on end of a great pattern, just need a window where it can occur.  Today is the first I have seen ensembles move off their spots.   Operationals are so different, that something had to give.  I generally don't expect snow around my neck of the woods until January or February.  We can get it earlier as we have had two great pre-Christmas snows(after going decades without those), but the norm is a six week window from Jan 1 to the middle of February.  So anything right now is a bonus.    If that 50/50 low is legit, that is important for the eastern half of the forum area.  

Not really. A southern slider is a great setup imo. Usually a -nao to allow that. Judah Cohen goes back and forth all the time. Yesterday he said no SSW event or anything and now he is saying a possible one if gfs to believed. Or start of one. I personally would like a track of mjo from 7-2 and take our chances from there, even in a weak mode

[Mr. Kevin]

20 minutes ago, Carvers Gap said:

Yeah, very different circumstance to get you snow vs MBY in many cases.  The EPS now has the pre-Christmas trough.  That is a legit window now I think.  PNA spikes positive temporarily for that model on the Euro.  We don't need weeks on end of a great pattern, just need a window where it can occur.  Today is the first I have seen ensembles move off their spots.   Operationals are so different, that something had to give.  I generally don't expect snow around my neck of the woods until January or February.  We can get it earlier as we have had two great pre-Christmas snows(after going decades without those), but the norm is a six week window from Jan 1 to the middle of February.  So anything right now is a bonus.    If that 50/50 low is legit, that is important for the eastern half of the forum area.  

I'm not greedy lol. I take icestorm or sleetstorm and be very content lol. Just some winter weather. 

[Carvers Gap]

3 hours ago, Mr. Kevin said:

Not really. A southern slider is a great setup imo. Usually a -nao to allow that. Judah Cohen goes back and forth all the time. Yesterday he said no SSW event or anything and now he is saying a possible one if gfs to believed. Or start of one. I personally would like a track of mjo from 7-2 and take our chances from there, even in a weak mode

I think the SSW has to be embedded in modeling somewhere as the high latitude blocking showing up seems indicative of that.  But beware, I have seen SSW fails and then modeling flip back warm OR the cold just dumps somewhere entirely different than originally modeled(could be better or worse).    We talked about volatility a week or so ago.  Very few things more volatile than an SSW showing up in LR modeling.  Literally nothing after the split is likely right.  Cohen is smart.  I haven't read any of his stuff this winter.  I quite twittering about four years ago, so I don't see a lot of what is on social media.  I probably should do that more, but just don't for whatever reason.  I follow Cosgrove on FB and that is about it....and I do this.  Feel free to share Judah's stuff though.  I may go catch his blog this evening now that you mention it.  I do like Webber and HM though.  Strong Twitter game for them.  Our mets in this region are the most accurate though.  

Snow in MBY can be from sliders, but our sliders have to turn the corner a bit in NE TN or Kingsport gets shafted.  Flow has to back for the most part.  Now JC and Bristol do just fine.  Bit of a rain shadow in Kingsport.  Our biggest snows are normally a trajectory from SW to NE for the snow axis.  Our biggest snows often tap the GOM and/or Atlantic.  I have found that big snows in DC usually involve lighter amounts here.  Middle and western forum areas often require different ingredients though not always.  Last year is a great example as middle and western forum areas got hammered...nada here.  Best snows here occurs on Arctic boundaries which have an axis which runs the Apps or SLP through the Carolinas which run from roughly Mobile and inside Savannah.   You all do better when the low cuts up the eastern valley - which sucks for us!   LOL.  

Chattanooga folks have multiple rain shadows, get the warm nose, and deal with system trending north whenever the opportunity presents.  Bama and Mississippi have done ok in recent years - I think.  Ah, and the dreaded dry slot in eastern areas is a bear.  

[John1122]

Looked like the 06z had a storm like Carvers mentioned, a low pops on an Arctic front and moves up through the Piermont and there's a statewide snow event to ring in the first day of winter. 

[Holston_River_Rambler]

There's a pretty big spread showing up on the EPS wrt temps, starting in about 7 days:

 

On Thursday the 23rd one extreme member has a high of 68 and low of 60, while on the other end, one member has a high of 19 and low of 8. It's normal for there to be increasing spread with increasing lead times, but that seems extraordinarily spread out, IMO. It seems like around the 18th or 19th something happens (or doesn't) that causes that spread. That's about when both the OP GFS and Euro start building the -EPO and -NAO, so I guess it just depends on how each member handles it. 
 

In fact, look at the spread for the EPO and NAO on the EPS:

 

A few members of both the GEFS and EPS showing some solid hits for parts of all of the TN Valley Christmas week, to go along with more favorable blocking. 

[Carvers Gap]

First off, thoughts and prayers are with those affected by the severe storms and tornadoes last night in western areas of our forum and in other sub-forums.  

Secondly, great discussion by everyone both in the severe thread and in this one.  Really hope the look in the 6z GFS continues, especially long term.  That is how you exit the warm pattern and maintain a winter one for a couple of weeks.  Not sure that happens, but the MJO would suggest the cold might hang on longer than expected.  Ensembles finally have the trough around the 21st.  That leads me to believe they are likely missing other amplifications.  As for the snow, I like that look.  No idea if it actually occurs, but both the Euro and GFS have something similar.  If the cold front is strong, that possibility exists.  As the trough enters the eastern US and leaves, that is the first window.  Real question then becomes whether a second shot of cold pinwheels in.  Some modeling drops it west, while others drop it into the nation's mid-section and scoot it eastward.  The GFS, as it did early last season, has the hot hand right now until the Euro takes the throne as the winter pattern stabilizes.  The CFSv2, though likely was a bit overdone, may score a bit of a coup if it gets cold prior to Christmas as it had the cold first.  Again, not my favorite model, but worth noting it has a warm-up after Christmas at 6z, and then another cold shot during early January.

So, I will keep it short for this morning.

[Carvers Gap]

If you really just need a lift this morning, take a look at the 6z CFSv2 control at 500.  Enjoy those.  You don't see that type of blocking every day on modeling.    

[John1122]

5 hours ago, Holston_River_Rambler said:

There's a pretty big spread showing up on the EPS wrt temps, starting in about 7 days:

 

On Thursday the 23rd one extreme member has a high of 68 and low of 60, while on the other end, one member has a high of 19 and low of 8. It's normal for there to be increasing spread with increasing lead times, but that seems extraordinarily spread out, IMO. It seems like around the 18th or 19th something happens (or doesn't) that causes that spread. That's about when both the OP GFS and Euro start building the -EPO and -NAO, so I guess it just depends on how each member handles it. 
 

In fact, look at the spread for the EPO and NAO on the EPS:

 

A few members of both the GEFS and EPS showing some solid hits for parts of all of the TN Valley Christmas week, to go along with more favorable blocking. 

This is why op runs will keep bouncing around the next few days, likely from one extreme to the other. Seems like that is often a precursor to a major pattern change, which the GFS at times seems to rush and the Euro at times seems to delay. 

[Carvers Gap]

4 minutes ago, John1122 said:

This is why op runs will keep bouncing around the next few days, likely from one extreme to the other. Seems like that is often a precursor to a major pattern change, which the GFS at times seems to rush and the Euro at times seems to delay. 

Yeah, well said.  Any guesses which way this heads?

[John1122]

16 minutes ago, Carvers Gap said:

Yeah, well said.  Any guesses which way this heads?

With the still falling QBO, the pattern we've experience in the past when it was below -20 in winter months,  the correlation between that and BN winters during Ninas, the cold November to winter correlation and the fact that our source region looks to be very cold, I think we flip cold at some point for an extended time. However, we have also seen a lot of climo that behaves the opposite of normal lately, so I'm certainly not confident. 

[Carvers Gap]

36 minutes ago, John1122 said:

With the still falling QBO, the pattern we've experience in the past when it was below -20 in winter months,  the correlation between that and BN winters during Ninas, the cold November to winter correlation and the fact that our source region looks to be very cold, I think we flip cold at some point for an extended time. However, we have also seen a lot of climo that behaves the opposite of normal lately, so I'm certainly not confident. 

Again, well said and thanks!   

[Carvers Gap]

Well, we have been waiting for the ensembles to jump on board.  The 12z GEFS....that is quite a change in the LR compared to just a couple of days ago.  Big trough late in the run.

[nrgjeff]

NWP has turned less hot for the 11-15 day. Do we want to ride the emotional roller coaster?

Convection is all over the West Pacific. Couple invests; however unlike last time, other deep convection is present. Maybe it will shake out well for some cooler temps in the Southeast US. 

Blocking tendencies are noted in the extended guidance, but it's probably a function of the MJO. Can it verify?

[Mr. Kevin]

24 minutes ago, nrgjeff said:

NWP has turned less hot for the 11-15 day. Do we want to ride the emotional roller coaster?

Convection is all over the West Pacific. Couple invests; however unlike last time, other deep convection is present. Maybe it will shake out well for some cooler temps in the Southeast US. 

Blocking tendencies are noted in the extended guidance, but it's probably a function of the MJO. Can it verify?

Hi Jeff. I'm hoping it can. I will take icestorm sleetstorm any winterstorm over tornadoes, which were terrible last night. Hopefully the pattern will adjust to colder and stormier eventually 

[Holston_River_Rambler]

1 hour ago, nrgjeff said:

Do we want to ride the emotional roller coaster?

Yes

I am ready for the highs and the lows and even a loop de loop in phase 7 for the next week, lol:

[Carvers Gap]

6 minutes ago, Holston_River_Rambler said:

Yes

I am ready for the highs and the lows and even a loop de loop in phase 7 for the next week, lol:

The official ale of the TN Valley sub-forum?

 

[Holston_River_Rambler]

2 hours ago, Carvers Gap said:

The official ale of the TN Valley sub-forum?

Maybe for Christmas, but I have a good Russian Imperial Stout saved up, brewed in TN, if we get some vodka cold. 

 

Here is also a semi on topic picture of what would have to be the ultimate 50/50 low, posted just for posterity  I've seen the GFS throw out some cray cray solutions, but this one would be wild. 

 

The ensemble has nothing like it, but what a wild NWP solution. I feel kind of bad posting the OP GFS at 384, but it is Saturday night and that is about as exciting as it gets here in Morgan County. 

[Carvers Gap]

The 18z GEFS ensembles have a whopper of a -NAO.  So, now we are beginning to see ensembles "see" the possibility for colder solutions in the LR.