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December/January 2019/20 Winter Speculation Thread

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All three operational (GEM, GFS, GEM) have it is some form or another.  The Euro is missing the cold high on this run...had it at 12z yesterday.  This is a storm that has been popping up on models suites for a few days if I remember correctly.  So, pretty good signal there.  Like we had a couple of weeks ago, the strength of that high is important with no blocking out front.  If we can get a 1040 hp over the top, lots of wintery precip is possible.  A 1050+ high would be crazy.  Still a long way to go...just like 30 more runs of the GFS.  LOL.  I will say that modeling does often pick up big events from decent range.  Is this one of those events?  I guess time will tell.  Looks like EPS/GEFS do have some support for this in terms of mslp placement.
This to me draws my attention, the large spread on the teleconnections at mid range (Control can't even keep its self in the 5% range). The Control goes -AO/-EPO/+PNA/-NAO lol. That spread looks like a 46 day EPS. Makes me wonder if we are starting to see any effects of the minor SSWE come into play on the modeling.3027dd1866b6fc1068405c1de14a0ff7.jpg

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^ Half joking but could be right on.

Late next week winter storm could be interesting in the true Mid-South (MEM/PAH) and a real CAD beast over in the Carolinas. If it even happens, I'm counting on WAA magic in the Valley to get KCHA* above freezing shortly after onset of precip. I hate that when it's snow. Love it when it bails us out of ice!

Still a day 8-10 event. GFS is slower than the ECMWF because the GFS gins it up stronger over New Mexico and Texas which slows it. 12Z Euro yesterday had energy from the Southwest but did not really get going until East Texas. Timing differences are not too important this far out. Main theme is NWP shows a chance of a winter storm. Other scenarios include drier cold or a cutter; so, I'm not too excited.

Regardless most all scenarios keep Chattanooga mainly rain, which I will always take over ice. If the Mid-South scores I'm hoping sleet and snow; less/no FZRA makes my job easier. I'll leave the Carolina CAD to the Southeast forum. Just keep that crap out of KCHA - unless all levels cold enough for snow.

*KCHA typically does warm up as fast as progged, but just CHA. From Athens north, including Maryville and Knoxville, cold tends to hold longer than progged.

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GFS wants to destroy MEM,Euro says, what cold?

 

FRI 06Z 13-DEC  -0.5    -1.3     129     110    04012     SN    0.00    0.00    
FRI 12Z 13-DEC  -3.1    -2.6     129    1948    05012     SN    0.12    0.00    
FRI 18Z 13-DEC  -1.0    -1.5     130    2479    06010     ZR    0.08    0.00    
SAT 00Z 14-DEC  -0.6     0.5     130    5135    05014     ZR    0.30    0.39    
SAT 06Z 14-DEC  -0.4     1.1     130    5696    04013     ZR    0.37    0.43    
SAT 12Z 14-DEC  -0.3     1.3     130    6963    05018     ZR    0.72    0.47    
SAT 18Z 14-DEC   0.1     0.1     130    5182    04015     SN    0.58    0.55    
SUN 00Z 15-DEC  -0.9    -0.5     130    2801    01014     ZR    0.30    0.59    
SUN 06Z 15-DEC  -2.7     0.1     129    4228    01010     ZR    0.12    0.59    
SUN 18Z 15-DEC  -2.5    -9.4     126       0    30010     SN    0.05    0.63   
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Modeling (euro/gfs) is generally doing a pretty good job from 144 hours out it appears.  Just toggling back through prior runs and they look to be generally accurate (placement of high to the north and low to the south) for the system projected through here in the next day or so.  I did notice a bit too much progression in the southern branch from the GFS and both look to miss the strength of the high pressure by several MB (1035 to 1037 from 6 days out, now projected to be 1030 to 1032)  I also noted the western ridge backing just a bit on modeling, especially the GFS.

Just a few things to watch as the 12z runs come in. This run of the GFS already has fairly sizable changes from 6z at 500....

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Even though the "big one" wasn't on this GFS run, still plenty to be encouraged about...the big high was there, but trailing.  Still a very active pattern with three pieces of energy in the pattern.  If that big high shows up, someone is going to pay the pipe in an active pattern IMHO.  Pay me now or pay me later. 

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And sure enough, the GFS finally finds its storm.  The key is whether that big high is real.  I think the southern stream is going to be active.  The CMC has a 1044 high on it...let's see where it goes.  Those big highs, for example, are similar to what caused the snow a few weeks ago.  The are potent.

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Oddly, I am not as worried about timing(maybe I should be)...just want that big high.  The two ingredients in a set-up without Atlantic blocking are an active jet and a good source of cold.  The GFS and CMS have those...and both have energy in the pattern at about the right time given the range we are at which is a week+.   

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While the bigger storm possibility still wibble wobbles, the GEFS has had an uptick in members showing a shortwave riding the early week front next week:
giphy.gif&key=e405fded4b608a3102266d2709e74b48ec4f8221782043d06f594b4a018d3e86
Euro OP is not too far off:
giphy.gif&key=45450d628ad613f159279d6f94cd36060a86044e7e143240a284bbb8f4f315a8 
giphy.gif&key=d2eaea8d688b02c3032eeb9520ecca1f931ade907f4dc333167d1a77ac1a54e7


I’ll take member #18 for one thousand Alex


.
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3 hours ago, Carvers Gap said:

And sure enough, the GFS finally finds its storm.  The key is whether that big high is real.  I think the southern stream is going to be active.  The CMC has a 1044 high on it...let's see where it goes.  Those big highs, for example, are similar to what caused the snow a few weeks ago.  The are potent.

I'm encouraged with how often those BFH (big friggin' highs) are showing up thus far. To your point, valley magic can and does happen with an active southern jet and a BFH. Still a lot of needle-threading necessary, but those factors at least keep us in the game. 

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One thing that's concerning to me is the trend of the AO on the Euro (12z GFS stepped closer in line). The downturn isn't tanking to neutral/negative as it was the past few days. With the AO trending more positive, we would need a stronger EPO/PNA ridge or combo to push the cold south. Setup on the 12z Euro favors the ridging getting us close to normal instead of torching)...GFS still is decent for a wintery setup. Hopefully that trend stops and starts correcting back the other way.

 

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93753151fd90f1d3aa3f653cb74c190a.jpg22b971def91e821ec6a3496b32b9843c.jpg

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It's really hard to get anything done here with an unfavorable Pacific.  But a favorable one can render the Atlantic meaningless.  

February 2015 was a +NAO/+AO combination. The Pacific drove the entire pattern. Big EPO ridge suppressed the storm track in the East and delivered major cold. Temps finished around -8 to -12 for the month in the region with multiple winter storms. 

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38 minutes ago, John1122 said:

GFS bringing shenanigans in a few days. 

sn10_acc.us_ov.png

Ensembles have some support. I counted 7-8 that had something. Member #13 just goes absolutely bonkers.

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Ensembles have some support. I counted 7-8 that had something. Member #13 just goes absolutely bonkers.
Yeah has a couple members that do, especially on the plateau..overall step in the right direction. c4fe25e32202ad64bbec822f7ec91eb5.jpg

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...And the 0z Euro w a tease way out there.  Interesting to see the models really looking to bring a system nearly due north out of the GOM at that d8-10 range.  That threat has never really materialized inside of d6 or 7.  With the sharp EPO ridge out West, it does make sense.  Would not be surprised to see one of those materialize in the d5-6 range sort of out of the blue OR just a thread that was "rediscovered."  Again, it is not uncommon for global models to lose storms around d7 and then find them again.

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Interesting battle this AM, as y'all have pointed out.

The GFv3S likes the little shortwave riding the front and many members of the 6z GEFS absolutely love the idea:

giphy.gif

To me, it looks like it depends on a tiny little shortwave riding down the Rockies and phasing with a bit of energy the main trough leaves back in the southwest. Now, not sure exactly how or if the 500mb vorticity can impact the jet, but there is more of a buckling that puts us under the right entrance region of a steak and keeps the lift going while we get moisture from the Gulf:

giphy.gif

One thing that is interesting about this to me is that the GFS Ensembles still use the old GFS core and can sometimes be less snowy than the new Fv3 that runs as the GFS now, but that is not the case here.

Euro keeps the energy more wrapped up in the main trough though, so everything is further north and there's less snow, even though there still is some precip. in the same time frame from some of the same processes:

giphy.gif

EPS though does offer some hope, and more than I've seen for this event from it:

giphy.gif

 

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As Holston mentioned...going to have to keep an eye on that the system Tuesday into Wednesday.   Both the 12z ICON and the GFS are touting 1040+ highs.  Reminds me of the system a couple of weeks ago.  Probably cold chasing rain...but that is big cold chasing rain.  Also, will it develop a wave along the front per the icon?

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It appears the 12z GFS has rediscovered the potent slp next weekend...amazing how that happens over and over again.  Now, it is a warmer system as their is a low in the Lakes.  But plenty of time for that to change.  For a progressive model like the GFS to have that.   My guess would be(if real) a more wound-up system further inland.  

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Pretty amazing how different the pattern looks with those big highs showing up in the Northern Plains.  Basically flattens the pattern out and prevents cutters on modeling...On the GFS, there are now three events to track inside of 10 days.  They are small but better than what we typically get at this time of year.

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It appears the 12z GFS has rediscovered the potent slp next weekend...amazing how that happens over and over again.  Now, it is a warmer system as their is a low in the Lakes.  But plenty of time for that to change.  For a progressive model like the GFS to have that.   My guess would be(if real) a more wound-up system further inland.  
Based off how the EPS has had a smaller variance with the teleconnections (especially the AO) compared to the GEFS being all over the place at longer ranges...I like the potential with that system (if the EPS can hold onto the sharp decline with the AO and a tad more Pacific ridging). Time it just right and the northern energy should dive into the southern system similar to what the 00z Euro attempted.

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22 minutes ago, TellicoWx said:

Based off how the EPS has had a smaller variance with the teleconnections (especially the AO) compared to the GEFS being all over the place at longer ranges...I like the potential with that system (if the EPS can hold onto the sharp decline with the AO and a tad more Pacific ridging). Time it just right and the northern energy should dive into the southern system similar to what the 00z Euro attempted.

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Yeah, I think the trick is just getting the big high since we don't have blocking.  Otherwise, those systems are going to zip right along.  On a positive note, there is some potential for over-running in terms of snowfall.  That cold will be stubborn to move.  Like John said, 14-15(could have been 13-14) had a winter with lousy blocking teleconnections besides the Pacific.  I have been thinking about the +AO data that you mentioned(great stuff BTW).  I just wonder if this is a year where the +AO might be a bit deceiving.  With a big EPO block, we essentially have blocking with cold air coming straight off the pole.  Now, a +AO most winters is a big problem...and I am not sure we will ever over-achieve like 14-15(to paraphrase Bob Chill I think), but I do think John has a point.  John and I used to argue back and forth at times(not really argue...just teasing really) about how important the Atlantic is in terms of blocking. Problem, is until the AO flips negative...the Pacific is the driver right now with marginal help from the Pacific.  So, he has sort of sold me on that, but I do like a good old fashioned -NAO....sort of like owning a Ferrari.  Nice to look at on modeling, but when the time comes...pretty much not something achievable by the common man.   I will also so, if we lose the Pacific...gonna get warm!  I do hold out hope that we actually do see some blocking over Greenland as we lose the Pacific.  That type of blocking might show up in mid-Jan per Nino climatology and this SSW stuff.  If we are able to steal December from the throws of warmth, we have achieved something in my book.  Pretty overwhelming how warm Nino Decembers have gotten in the past.  That said, there are some colder clusters though smaller in number.

 

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February 2015 was fabulous here as most know, with close to 40 inches falling in just over a 3 week span.

     The +TNH pattern along with one l.p. after another hooking with the +NAO was remarkable. The constant succession of Lps tracking up thru eastern Canada acted t in a way that kept the +NAO from behaving as usual in the they pulled the air southward from it instead of underneath and eastward. 

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ECMWF seems to like a second back piece of energy near/post frontal (Tuesday) even if it's weak. Wobbles between still mainly rain, or a chance of snow I-40 north (and Plateau). Can't see any path for Chattanooga though.

My next post will probably be on Monday. Hard to feel anticipation when I've got Chatty near 0% but I'm always happy for members up north (or northwest) who get snow. If this one craps out, the pattern remains cold-ish for several days after fropa with East troughing.

For now, have a good weekend!

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Pretty amazing how different the pattern looks with those big highs showing up in the Northern Plains.  Basically flattens the pattern out and prevents cutters on modeling...On the GFS, there are now three events to track inside of 10 days.  They are small but better than what we typically get at this time of year.

Small/weak typically means less WAA also


.

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Yeah, I think the trick is just getting the big high since we don't have blocking.  Otherwise, those systems are going to zip right along.  On a positive note, there is some potential for over-running in terms of snowfall.  That cold will be stubborn to move.  Like John said, 14-15(could have been 13-14) had a winter with lousy blocking teleconnections besides the Pacific.  I have been thinking about the +AO data that you mentioned(great stuff BTW).  I just wonder if this is a year where the +AO might be a bit deceiving.  With a big EPO block, we essentially have blocking with cold air coming straight off the pole.  Now, a +AO most winters is a big problem...and I am not sure we will ever over-achieve like 14-15(to paraphrase Bob Chill I think), but I do think John has a point.  John and I used to argue back and forth at times(not really argue...just teasing really) about how important the Atlantic is in terms of blocking. Problem, is until the AO flips negative...the Pacific is the driver right now with marginal help from the Pacific.  So, he has sort of sold me on that, but I do like a good old fashioned -NAO....sort of like owning a Ferrari.  Nice to look at on modeling, but when the time comes...pretty much not something achievable by the common man.   I will also so, if we lose the Pacific...gonna get warm!  I do hold out hope that we actually do see some blocking over Greenland as we lose the Pacific.  That type of blocking might show up in mid-Jan per Nino climatology and this SSW stuff.  If we are able to steal December from the throws of warmth, we have achieved something in my book.  Pretty overwhelming how warm Nino Decembers have gotten in the past.  That said, there are some colder clusters though smaller in number.
 
At work right now, but I have all the data with Decembers, back to 1950, where the AO went 1.5 or higher for a monthly mean. Data was fairly interesting...Decembers where the EPO or PNA had favorable spikes (or combo of both)..we were able to remain near normal or very slightly above for the avg monthly mean temp at TYS. Decembers with a non favorable Pacific blowtorched big time. When you break it down to include ENSO, QBO, NAO etc..NAO state had widely ranging effects (same with QBO). So NAO and QBO I give little weight to regardless of state...(now I do believe when the southern jet is active and the Pac is favorable or needs some minor assistance, then the NAO begins to gain more weight. Can't remember 14/15 off top of my head, but I believe it had periods where the EPO went -300 or higher plus it was at or near one of the most -QBOs ever recorded for DJF.

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