Winter Speculation 17/18 -December Thread

[Carvers Gap]

Here is what I am talking about.  Hey, it may be true.  The Euro has tried previously dumping cold in the West but usually east of the Rockies...but in this case it again finds a way to dump cold under a ridge into Southern California.  The small piece of energy in slide one turns into the massive trough in slide two.  It was absent(edit...detached) in the AM run.  I placed a question mark in the middle of the country, because that is just a mess of a run IMO due to what happens downstream.

[PowellVolz]

...and then the 12z Euro.  Great example of the butterfly effect.  The trough in NA finds a way to interact with a smallish piece of energy in the eastern Pacific.  That piece of energy then becomes a gigantic cut-off low and sends BN temps west of the Rockies.  It basically replaced the ridges with troughs and trough with ridges over the lower 48 from d7-10.  I usually never toss a run and won't this one either...but I am tempted.   The overall NA pattern is the same...but the downstream lower 48 pattern is greatly disrupted by the cutoff that comes into Washington.

Doesn’t the euro hold back energy as a bias? Would that be its hiccup?


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[Carvers Gap]

Just now, PowellVolz said:

 

Doesn’t the euro hold back energy as a bias? Would that be its hiccup?


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Yeah, it likes to hold energy in the southwest.  Sometimes it is right, but usually it is over Four Corners.  I mean Seattle gets big storms like this...but rarely does the cold penetrate to Baja even w the bias.  I think there is some pretty cold air about to enter the pattern.  I always forget one of my own wx rules which is...the models can get very erratic when low level Arctic cold enters NA.  It is almost like the models can't "see" it....but the effects above the cold air it can see.  And then things go haywire.

[Carvers Gap]

39 minutes ago, John1122 said:

The GEFS doesn't bring the -NAO but keeps us locked in the Pacific driven freezer, ala Jan into Early March 2015. It's a pattern that can really stagnate with brief breakdowns. That run on the GEFS has the region above normal for 3 of the next 16 days. 

The NAO can aid even further but it's not needed for Southern storms. The storm a few days ago snowed way south and east of here with a +NAO. The NAO was predominantly positive in Jan-Mar 2015 as well. It was also predominantly positive in the very snowy Jan-February 2016. Granted that year was very latitude driven, as basically border counties with Kentucky/VA and points north were hammered while areas south of there were slightly too warm for most storms. 

If given a choice between a -NAO and a cooperative Pacific I'll always take the cooperative Pacific.

The Pacific has made for some good winters during this century.  The -NAO can produce big Noreasters, but like you say...our big storms are not always from the GOM.  We get sliders and waves, etc.  I like the -NAO because it slows the pattern down.  It just makes forecasting big storms a little easier because the moving parts slow down.  

[Carvers Gap]

Tagging onto Powell' s post....I also like the tendency for West Coast storms to exit the East coast at the same latitude they enter the continent.  So, just assuming the Euro is correct w that small piece of energy(and it is prob wrong), the storm would enter the US at the latitude of roughly Oregon.  That means the storm probably takes the low road(assuming the Euro bias is in play), rolls south through Texas and then to Jersey say d12-14.  That looks a lot like the GFS at noon.

[John1122]

33 minutes ago, Carvers Gap said:

...and then the 12z Euro.  Great example of the butterfly effect.  The trough in NA finds a way to interact with a smallish piece of energy in the eastern Pacific.  That piece of energy then becomes a gigantic cut-off low and sends BN temps west of the Rockies.  It basically replaced the ridges with troughs and trough with ridges over the lower 48 from d7-10.  I usually never toss a run and won't this one either...but I am tempted.   The overall NA pattern is the same...but the downstream lower 48 pattern is greatly disrupted by the cutoff that comes into Washington.

We will see what happens. I don't usually put a lot of weight on model runs that don't make much sense or that show unusual solutions that don't fit the pattern.

[Carvers Gap]

28 minutes ago, John1122 said:

We will see what happens. I don't usually put a lot of weight on model runs that don't make much sense or that show unusual solutions that don't fit the pattern.

Yeah, agree.  Was noting it since it showed how one small feature can really effect the run.  Likely that feature will not have that impact in later runs.  The ensembles hopefully will support a pattern that makes more sense.

[nrgjeff]

I'm not too concerned about that horrendous Euro and Ensemble run. Probably too hung up on that California (dreaming?) trough. Tomorrow hope it goes away on all the Euro products. Actually either way it is slowly bringing the cold east.

Broader themes from above, yes the PNA is our number one driver with highest correlation coefficient. Gladly trade in the NAO for the right +PNA. 

[Carvers Gap]

Yep, Jeff.  The 12z EPS is back to the trough under the ridge solution out West d10-15.  Making my neck hurt w this many swings.  

[Carvers Gap]

Just do yourself a favor and go look at the 18z GFS.   May or may not verify.  But go look.

[Carvers Gap]

There is a 1050 hp coming south from central Canada at 240.  Already cold here.  Snowstorm modeled at d9. At 252, a 1052 hp is over the Dakotas.

[PowellVolz]

Just do yourself a favor and go look at the 18z GFS.   May or may not verify.  But go look.

Id cash out right now.


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[Carvers Gap]

3 minutes ago, PowellVolz said:

Id cash out right now.


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No doubt.  1051 hp over Iowa.  Trough shaped like a bowl.  It may snow in Tallahassee.

[PowellVolz]

No doubt.  1051 ho over Iowa.  Trough shaped like a bowl.  It may snow in Tallahassee.

The next system looks like a monster on Christmas night I believe. A little warmer at the surface though.


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[Carvers Gap]

Just now, PowellVolz said:

The next system looks like a monster on Christmas night I believe. A little warmer at the surface though.


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That is a total mess righ there.  Wow.

[PowellVolz]

That is a total mess righ there.  Wow.

If mods are still figuring out what’s going on with the EPO, the cold air could possibly be further south than modeled.


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[Carvers Gap]

Now, John.  That might be 1989 worthy or 83-84.  

Ya'all, I know it is one run....but that gets here around day 9. That is not way, way, way out there.  It is just way(a single way) out there.  What a run.

[J.C.]

This is far out there, but what a difference in just a couple of days.  If anything even close to this comes to fruition it would be a giant mess.

[John1122]

The 18z is very similar to winter 2015 when we had a near valley wide snow event followed by zr due to a big arctic high driven by a -EPO Ridge. So since the look at 500 is similar, seeing similar stuff from the model is not a surprise. 

[John1122]

The insane clown map is showing all frozen as snow down in the 3 feet areas. It'd be a horrific ice storm rather than a mega snow dump. 

[jaxjagman]

We're due for a major ice storm unfortunately.Seems like a perfect set up for it with systems coming up from the SW.Chances for moisture looks decent the next upcoming weeks we just need cold air.Seems like to me this is the best potential for a winter storm or two we've seen in quite sometime upcoming.

[John1122]

00z brought a monster SE Ridge back with the odd trough from sw to ne. Doesn't fit the pattern with the mega -EPO but we'll see what comes to pass. 

[BlunderStorm]

The GEFS takes a step back to supporting a more robust non-transient ridge across the east coast. The likelihood of a week or two of above average temperatures with lack of activity winter wise is seeming more likely. If viewed as a pendulum however a pattern change would occur in the heart of winter. On the bright side a strong -EPO is shown along with a -AO a little later. A common unfavorable theme however is a consistent +NAO

[Carvers Gap]

Most have already covered the overnight runs.  Two of the last three days have had model runs with a big SER on several models and runs.  Probably time to include that as "real" in my thinking for the 8-15 day range.  It is moving forward in time and formidable once in place on both operationals and ensembles.  It really does not want to move.  The 6z GFS operational even tries to incorporate the 12z Euro from yesterday with the small storm becoming the trough.  For whatever reason(and I have no explanation except that maybe the ridge is so tall), the models are trying to tuck a massive trough under a -EPO ridge and the cut it off.  I still think the Euro is up its usual bias of trying to stick energy in the southwest.  But it cannot be discounted as a possibility since the 6z GFS basically did the same thing....sometimes the cold goes into the southwest as a cutoff, just usually not under a -EPO.  So, I will roll w a JB quote here and I prob agree...the -EPO is either not the real deal, the MJO from two days ago was wrong, or the models are in error sending that trough into the southwest and holding it.  What is worse...the overnight model runs almost appeared to be a pattern change.  Either way the SER is something that we will have to deal with it appears.  And the idea that the cold goes West (even west of the Rockies) is a real and even probable solution now.  The EPS for the second straight run was a torch for the East.  And I usually don't use the term torch.  My hope now and maybe it is wishcasting at this point, is that the models don't see the low level cold or that the cold highs will overcome an expansive SE ridge.  

[Carvers Gap]

I went back and looked at both ensembles and operationals from 0z to now.  The configuration of a trough in the southwest stretching to Greenland under a strongly negative EPO ridge is a common theme.  The Euro goes bonkers with the idea due to its southwest bias idea.  But it was the GFS that sniffed this out last week when it switched to depicting the cold front stalling from TX to the Midwest.  The GEFS does show cold heading eastward, but is seems locked at d14.  Remember when the cold stopped in time on the models earlier this week?  That is a signal for me that the models are jumping the gun.  I am now 50/50 on whether this is a pattern change now.   The big SER is now well within ten days, so it is likely on its way.  The GEM, EPS, and GEFS all depict a trough stretching from the Southwest (sometimes including the Baja) to Greenland.  I truly want to discount this look as it just does not make sense....but the preponderance of model evidence is now forcing me to have to accept that it is a possibility and might even be a likely one.  Pretty sure there are very few instances (I cannot think of one) where this pattern locks and holds....but the major global models are doing exactly that.  This is not d10-15 anymore.  This switch begins in six days at the latest.  Below is the 6z GEFS since it seems to be a happy medium between the GEPS(Canada) and the EPS(Euro). #1 is the trough east of HI.  It is a signal for eastern snow and cold.  #2 is the -EPO ridge.  It is a signal for eastern cold and snow.  #3 is the trough under the -EPO ridge.  It should be kicked eastward by features one and two.  #4 is the downstream SER which does not teleconnect to either one or two.  #5 is BN heights over the Davis Straits which is a +NAO.  That does signal warmth in the East....but does not appear strong enough to force cold under a western ridge.  Maybe the EPO ridge is so tall that is is not in fact a true EPO ridge but will verify as AN heights in the Arctic?  

[Carvers Gap]

One last thing...and then I am done for the AM.  It is possible that the cold is being under-modeled.  That is a realistic possibility.  If those big highs are present, it could push the cold into the TN Valley.  Read a bit of JB from last night.  Sometimes those 500mb maps miss how far truly cold air can travel.  But even he is realistic to the idea that the EPS is now consistently showing big warmth in the medium range.  In the east side of the valley this is a stretch....but the west side might actually see winter wx.  They are not out of it.

[PowellVolz]

That was some ugly overnight mod runs.


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[AMZ8990]

10 minutes ago, PowellVolz said:

That was some ugly overnight mod runs.


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Yeah it was, it's a good thing it will flip flop in a few hours though! Lol.  

[John1122]

12z has beaten back the SE Ridge to some extent again. 1037 high over N. Illinois lets the cold slip enough south to allow ice in the southern areas of the forum by December 23rd. Long duration ice event in southern Texas. Huge 1047 HP sitting over British Columbia for a big +PNA.

[John1122]

By 240 an ice storm is underway south of 40 down to the state border as a LP is slowly moving across Southern Texas. 1040 HP sitting over Chicago funneling down low level cold.