December 2018 Pattern And Forecast Discussion

[Holston_River_Rambler]

I can't find the EPS weekly mean

 

 

 

but the Euro control run at 45 days gives us all a Christmas present: https://imgur.com/a/GfgXoCn 

Most of that comes between days 30 and 45. I went through each of the EPS members 0-45 days snow totals and any that give big totals, give most of it after day 15. Maybe a hint at the time frame for the pattern change at least.

[Carvers Gap]

I was not a huge fan of the Weeklies run.  It cut snow totals by about half w a fairly decent "warm-up"(likely rainy and cloudy) in the middle.  Looks like a decent cold shot from Jan 4-11 and another from say January 23 - the end of the run.  The worst of the cold was pushed back.  Likely culprits?  Maybe the MJO is over-riding the Nino signal.  Also the SOI is in La Nina territory and decently so.  That is rare and is not a good thing.  While it wasn't a Grinch run and certainly wasn't terrible, it did have a lump of coal or two.  I certainly don't like to see AN temps during our best snow climatology time.  That said, if we get cold during the last week of Jan into February w this constant precip...have to think that is good.  My rule about Nino winters is that they just require a ton of patience...I am not fan of backloaded winters.  At this point, I don't see anything that would change my original winter set of ideas.  Below is the teleconnection chart.  There are certainly some inconsistencies there.  

[Carvers Gap]

And yes, the control was very nice which likely reflects the nice AM run that the Weeklies were derived from.  The mean...well.  I generally roll w the mean....but that might signal that there is come "conflict" within this run of the model.

[Carvers Gap]

And I will admit that I am always a little bit wary when the best part of the pattern keeps getting pushed back.  Overall, I think Jan will like finish around normal or a maybe slight above for temps.  That is not always a bad deal for snow.  That time from late during the third week until the end of the run looks prime.  Maybe we can steal a storm prior to that time frame.  One good thing is that when it has gotten cold, it has snowed somewhere in the forum area.  I wold think the Jan 4-11 time frame might actually favor the western 2/3 of the forum area(and that fits the Nina SOI) while the lat Jan-Feb time favors the eastern 1/3 (when the Nino signal finally takes over in terms of temps).  That is about it....next run will likely be different as someone correctly noted that the strat stuff is probably a wrecking ball on LR models.    

[Carvers Gap]

And Merry Christmas to the best wx subform on the planet.   With that in mind, here is a likely culprit (again, a friend pointed this out) in why the Weeklies are swinging so much.  Keep in mind that if we get blocking that induces cold, that is likely about two-three weeks after the split.  That does align quite nicely w the Euro.  Anyway, if we learned anything from last year's split...model mayhem is probably going to be a constant until it splits.  Welp, back to Christmas stuff.  Unless something changes drastically or unless there is a question...I am probably not posting tomorrow(but who knows?).  Looks like the big question is now where does the cold go as Jeff pointed out above...

 

 

 

[Holston_River_Rambler]

I saw a met on another board yesterday say (at least part of) what you just said (in first post of the three). Temporary cool down first week of January, then another Pac jet extension second week = one more warmup, then the shift.  His/ her speculation was supported by a east asian mountain torque event forcing a Siberian high south, that is closer in time to now, so easier for models to forecast and maybe closer to reality. Looking at the 00z Euro that formed the last weeklies run (0z 12/20), sure enough it is less intense with the Pac jet than today's 0z run. So that may have had an impact. 

At this point I'm willing to say I bet it gets worse (modeling) before it gets better. But I think it will get better. Big(ish) SE ridge (tempered some by base state unlike last year's) aided by Nina SOI and MJO forecast to be literally off the charts in phase 6 (at least as the GEFS sees it). I do think the MJO reality ends up closer to GEFS than Euro/ EPS, but not as amped as today's run. I think the SPV ends up shredded, split or not, but not speculating on impacts since I've seen too many people 1000x knowledgable than me worried about exactly how it all percolates down to 500mb. 

Now I will say if the SPV is shredded, and the MJO gets to 8-2 phases, all that is ingested into the models, and then everything is still getting pushed back, I will be worried. 

Ponied up and bought a model subscription service, but can't find the EPS mean snow like I posted a few days ago. I will say looking at individual city's means it does look less robust than the last run, as you noted and would be expected with what we've been discussing. 

[Carvers Gap]

4 minutes ago, Holston_River_Rambler said:

I saw a met on another board yesterday say (at least part of) what you just said (in first post of the three). Temporary cool down first week of January, then another Pac jet extension second week = one more warmup, then the shift.  His/ her speculation was supported by a east asian mountain torque event forcing a Siberian high south, that is closer in time to now, so easier for models to forecast and maybe closer to reality. Looking at the 00z Euro that formed the last weeklies run (0z 12/20), sure enough it is less intense with the Pac jet than today's 0z run. So that may have had an impact. 

At this point I'm willing to say I bet it gets worse (modeling) before it gets better. But I think it will get better. Big(ish) SE ridge (tempered some by base state unlike last year's) aided by Nina SOI and MJO forecast to be literally off the charts in phase 6 (at least as the GEFS sees it). I do think the MJO reality ends up closer to GEFS than Euro/ EPS, but not as amped as today's run. I think the SPV ends up shredded, split or not, but not speculating on impacts since I've seen too many people 1000x knowledgable than me worried about exactly how it all percolates down to 500mb. 

Now I will say if the SPV is shredded, and the MJO gets to 8-2 phases, all that is ingested into the models, and then everything is still getting pushed back, I will be worried. 

Ponied up and bought a model subscription service, but can't find the EPS mean snow like I posted a few days ago. I will say looking at individual city's means it does look less robust than the last run, as you noted and would be expected with what we've been discussing. 

Man, a wx model subscription is likely some of the best money that I have spent.  I really enjoy it.  Great discussion BTW.  And yes, model mayhem probably will be a given due to the potential strat split.  So, a huge grain of salt should be taken for my comments above.  LOL.  

[Carvers Gap]

And I know just enough about mountain torque to be dangerous!  LOL.

[Carvers Gap]

When I am no longer talking about a 4-6 week long lead forecast...I will know that we have hit a good spot!  Hopefully that ends during the Jan 4-11 time frame.  Took a quick jog over to the MA forum.  They liked the 18z FV3 run.  Indeed, that is a cold, cold run.  Maybe we will have something to discuss soon...certainly might be so if that run were to even remotely verify in terms of temps and storm track.

[AMZ8990]

11 hours ago, *Flash* said:

I itch for something to track. Even if it’s a 1/6/17 repeat, I’ll take it at this point. 

I’ve Been thinking the same thing!

[Carvers Gap]

Well, I was going to hold off posting today.  Bit of a lull right now in the Christmas activities....the 0z EPS d10-15 time frame was pretty nice.   All I have to say.  

[AMZ8990]

14 hours ago, Carvers Gap said:

When I am no longer talking about a 4-6 week long lead forecast...I will know that we have hit a good spot!  Hopefully that ends during the Jan 4-11 time frame.  Took a quick jog over to the MA forum.  They liked the 18z FV3 run.  Indeed, that is a cold, cold run.  Maybe we will have something to discuss soon...certainly might be so if that run were to even remotely verify in terms of temps and storm track.

  Yeah there’s some serious cold on the far end of the hr spectrum on the FV3.  A good portion of the country would be Below freezing for a few days if it came to fruition. 

[John1122]

This one has been on again off again, but this is a great New Years look, I'll be in Chattanooga per usual, so 40 and North may as well get ready for flakes. 

 

[jaxjagman]

I'm visiting in Florida for a few more days.Let's hope the euro is doing it's bias and trying keep it out of 6,GEFS is showing a 4 sigma,strong MJO signal

[jaxjagman]

Hard to tell right now,looks like the Euro might be right but we'll see,strong signals into the Maritime but after that the signals could get weaker after that

[Math/Met]

A major mountain wave event is possible for Thursday into early Friday morning for the foothills of East TN.  Models are consistent with bringing a southerly 60-70+ kt LLJ across parts of TN and KY, with the strongest core of the LLJ just to the west of the mountains. This puts East TN mountains in a favorable spot. Winds below 850mb are from a southeasterly direction and that will establish the cross barrier flow within a stable boundary layer.  This system and forecast soundings look like a classic set up, so I think damaging wind gusts are likely along the favored mountain and foothills locations.  

[John1122]

Canada is looking like it's going to get frigid soon. -10s to -30s closing on on the borders with the US and repeated shots of it on the FV3.  So there won't be much, if any waiting on Canada to reload cold. It doesn't take long with maximum darkness over the source areas. 

[Carvers Gap]

Interesting to see differences in the EPS and GEFS right now.  I think how the American model and Euro model handle the MJO(see Jax's post above and JB on twitter) is causing big temp differences in the LR.  The GEFS enters phase 7 at very high amplitude.  The Euro(don' think that is the ensemble...but still gives a good picture of things) is at lower amplitude which correlates to less extreme cold.  Both show a trough in the East...but how cold they will be is a big question.  The FV3 as John noted is frigid late in run.  I suspect the Euro is trying to catch-up just by the way its graph looks.  The GEFS is likely too extreme, but it nailed a similar look last winter(think it was last winter anyway....could be the one before).  But if we were to hypothesize that the Euro is too low in amplitude and the GEFS is slightly to much, and blend the two...That is a very good signal for January assuming the MJO goes into phases 7,8,1,2 at decent amplitude and does not crash into the COD.  Overall, nice trends.  My only "concerns"(might be too strong of a word) is that the trough in the East is centered too far eastward which means storm confluence would be in the Atlantic and that the source region is a problem(good trends past couple of days though).  We need to NAO to kick-in.  If we can get the strat perturbed(don't necessarily even need a split...but don't want it wrapping back up either!), that might induce blocking over Greenland.  The 6z GEFS has just enough blocking to make things interesting.  I probably lean towards the GEFS on this set-up simply because it handled it well early last spring.  

[Carvers Gap]

I think something else that is noteworthy is how much precip is forecast for the Eastern Valley including the Plateau, especially the Plateau.  Frozen or not, that is A LOT of water to fall on already saturated ground.   

[Carvers Gap]

This is not a WAR(Western Atlantic Ridge) like last winter but from memory it seems to have a striking resemblance to that very feature that preceded the strat split late last winter.   I am not an atmospheric physicists, but I suspect ramming this type of air into sub-Arctice/Arctic regions does not have a benign influence on the PV(even though this is just at one level of the atmosphere...the PV is a 3D entity of course).

 

Judah Cohen has a nice animation of the potential split...maybe three vortices.   A parent and two daughters?  (sounds weird...but that is what several are terming that look). Have to think that look is goings to slow things down at high latitude and induce long term blocking.

 

 

[Holston_River_Rambler]

In terms of the MJO, I found this on another board. This is one time I feel a little bad about taking something since it is experimental, but then again, I think we are just using it for research purposes, so why not?

Experimental progression of the MJO on BOMM with ensemble mean, spread, and probabilities. The BOMM depiction seems like a nice compromise between the Euro and GEFS, just hope it doesn't go into the circle of death at the end:

 

Also saw some discussion from Eric Webber that the MJO will likely amplify more due to feedback from the SSW descending to the tropics. Maybe that is also what we saw last year. 

Also yay, I finally got a gif to embed!!!!

[Holston_River_Rambler]

I think the Jan. 3 - 5th time frame is our best shot in the foreseeable future and I think NW areas are favored at this time, but could change at 8+ days. Last in a train of southern stream waves, so a good fit for TN valley as the baroclinic zone (hopefully) gets further SE with each wave and front. Details seem dependent on N. stream suppression/ cold available and we saw how wonky that N. stream energy could vary from run to run with the Dec event. If the SOI is still Nina-ish (not sure how to check it) maybe that has an impact on the speed of the ever fickle N. stream? 

Another thing to keep in mind is that most systems have been verifying with more precip. and more amp last minute, so hopefully this last wave can give some of us an appetizer for what will hopefully be more board wide opportunities as we move into mid - late Jan and Feb. This wave does seem like it will herald a bit of a pattern relax before whatever effects the strat, MJO cycling, etc... start to percolate and the last wave before a relax is usually good for us. 

Interesting that the GFS (suppressed, but the energy is there)/ Fv3 have the energy even though the GFS/ American ensemble suite has the MJO at some insane amp in phase 6 at that time. Several of the GEFS ensemble members have the storm, though some seem to delay it.  The Euro as of today at least is more bullish on the 3 -5th period, but has the MJO in the COD at that time. Wondering if the forecast phases/ amplitude have an impact on how models resolve details of patterns at range. If so, pretty neat that our base state may be so chilly/ southern stream strong that even high amp phase 6 offers at least a chance. What will these models be showing when we get back to phases 8-2?

Edit: went through and looked at the ensembles after seeing Bob Chill mention the control looking like the Op. Most of the ensembles for theJan 3-5 event look suppressed, which I'll take at 8 days. The further that front get get, the better IMO (maybe I'm being a little selfish for Knoxville). Now watch me eat that when it ends up suppressed. 

[Carvers Gap]

For the last several runs (4+ or more) the EPS has trended towards less AN heights over AK and today the 5d mean is BN.  If you were to give me one feature that I feel is a "no go" to long term cold in the East...it is BN heights over AK.  Not only that but it is lowering heights near Greenland.  Not a great run. We want that trend to stop during the next runs and hope it is a blip OR we need that ridge to roll on through, and a trough develop in its wake.  I will say that it does fit the Weeklies "lull" from Jan 11 to Jan 23rd as shown on Monday's run.  But I do know this, once established, BN heights over AK almost always take longer than the models depict in moving them out.  Again, main concern today is that the trough is just too far to the East on the EPS.  Looking more and more like our opportunity for winter will be week 4 of January through February if the EPS is to be believed.  And hey, that is not a bad window. In '96, that is was when the hammer dropped.  And since we are still talking d10-15 weather....we are not in a great winter pattern yet.  The Jan 2 time frame has me marginally interested for now.  I do think we see some decent cold from Jan 4th-11th, but a true wintery, sustained pattern may be 3-4 weeks out if the EPS is to be believed.   Now, the GEFS does give us a great shot at a great January.  We need to be pulling for the GEFS to be right!  And there are reasons to believe the GEFS as the EPS has been infamous this winter for missing amplification of cold and troughs in the East.  Honestly, I give them equal weight where during normal circumstances I would weight the EPS at 80%.  I think the MJO divergence between the two models is creating two very different solutions in terms of the 500 patterns. 

[Carvers Gap]

Excellent poster with very good comments about the model discrepancies that we have recently seen.  Not a long write-up...but on the money IMO.

 

[Carvers Gap]

There are times when the Euro seems to struggle....SSWs, when fresh Arctic cold begins to invade the mid-latitudes of NA, and w high amplitude MJOs.  It is worth noting that the GEFS/GFS suite handled the strat split last year pretty well.  I think ignoring the Euro is unwise, but it is also fair to note when it can have problems.   Also, I have noticed throughout the years that the GFS has a bit of a cold bias in the LR.  So, if we take the model biases at face value....the Euro is probably too warm and the GEFS is probably too cold.   I think Don's post above pretty much covers the situation.  I will also add that betting the Nino pattern is playing with house money.  So, if we ride climatology...we probably come up with good guidance:  warmish interlude, backloaded winter, coastal storms, blocking.  IMHO, the only thing that might throw a wrench in this is the SSW.  Without it, we are money IMHO.  With it, it could accentuate already decent climatology or nix it if the cold goes to Asia.  I suspect it will enhance high latitude blocking or at least cause its duration to be longer.  

[nrgjeff]

Hard to deny the big cold pattern (after day 10) keeps being delayed, like a connection from ATL back to CHA. Appears the cold air supply is scouring out due to Chinook wind, a risk with Alaska ridges oozing into western NA.

Weeks 4-6 show more Greenland type ridging which might work better, IFF it verifies. Pushing to the back half of January or even early February is still prime snow season, in spite of slowly rising normal temps.

Belated Merry Christmas! Hopefully a happy snowy New Year! ❄️ 

[jaxjagman]

MJO still looks strong on the GEFS but not the euro,it still looks to have weaker signals past the maritime

[jaxjagman]

1 hour ago, nrgjeff said:

Hard to deny the big cold pattern (after day 10) keeps being delayed, like a connection from ATL back to CHA. Appears the cold air supply is scouring out due to Chinook wind, a risk with Alaska ridges oozing into western NA.

Weeks 4-6 show more Greenland type ridging which might work better, IFF it verifies. Pushing to the back half of January or even early February is still prime snow season, in spite of slowly rising normal temps.

Belated Merry Christmas! Hopefully a happy snowy New Year! ❄️ 

I was hoping to head back to Tn tomorrow and hit maybe some storms around the big bend area of FL,gonna visit a school bud guess ill just drink beer maybe catch a spout at his house if i'm lucky Thought this would be better,talked my old lady and kids into flying back and i was going to visit old friends and drive...boooo

[Carvers Gap]

1 hour ago, jaxjagman said:

MJO still looks strong on the GEFS but not the euro,it still looks to have weaker signals past the maritime

Great comparison graphic.  Gonna call that GEFS MJO "A Header" because it is erasing the header due to being so anomalous!!!  If that Header verifies, we are likely in business...though I don't like the MJO heading for the COD.  If I remember correctly, that pattern ended winter last winter...but it also seemed to precede the strat split.  Now, I am NOT calling for the end of winter.  Though a wall-to-wall cold winter is probably not in the cards anymore either.  That said, if/when the strat split occurs, then we will have a better idea of where this goes.  Just no good bets on my part as those things sort of have random affects...but many times they reset the pattern.  I give that split about 14-16 days before it begins effecting things at this latitude(bout the third week in January).  If we can get last year's blocking this year(about five weeks earlier than last year), then things might get interesting...even very interesting.  As Sutherland noted, the Long Paddock site now has the SOI negative at -3.32.  That is a significant change.  Its positive nature has likely been symptomatic of lingering Nina atmospheric conditions.  IF it stays negative, that likely means the Nino has FINALLY taken over, though all of this wet weather already says that it has.  And remember, my memories of El Nino winters are of cold rains w highs in the upper 40s/low 50s w lows barely above freezing for large portions of winter.  But there have been some notably good Nino winters.  Best case scenario is that that the GEFS goes into phase 7 at high amplitude and takes the tour of the cold phases, crashes into the COD, and strat split affects take over w Greenland blocking.  Worst case scenario is the Euro MJO is correct which means that it goes into the COD before it gets cold, it cycles back into the warm phases, the strat split doesn't happen, and we go warm until early to mid Feb.  If forced right now, I would just blend the two scenarios...GEFS is half right w the MJO as the Euro is too weak and too quick into the COD but the verification is a weak passage through at least some cold phases, a  non-textbook strat split, and a muted warm spell during prime snow climo of mid January, and finally, February living up to Nino climatology with being cold and snowy.  Again, these types of winters require so much patience.  In some cases, Nino winters don't even begin until about the time folks start getting spring fever!  

So, no changes on my overall seasonal ideas...I compare these scenarios to fishing the Madison out West around $3 Bridge.  We get to the river at around 6:30 or 7:00 in the evening.  The caddis(insects) are flying around in the sage just above us.  We plop down on the bank while looking for heads to rise.  We are not in a hurry.  Many folks have already loaded up and gone home, but this stretch of river holds a secret for those patient enough to wait.  If we get lucky, we net an early fish.  Those are often rainbows.  Then we wait, and we wait, and we wait.  When it is almost dark and the air has cooled, the caddis come down to the water to lay their eggs.  We position ourselves so that we are looking directly into the glare of the moonlight or fading sunlight or from the quickly dimming blue overhead reflecting off the dark water.  Then, a stealthy head pokes out of the water and starts sipping caddis off the top.  We may only land one or two fish, usually browns, but they will likely be nice fish.  The micro-currents create all kinds of un-natural drag...but on good evenings things can come together.  The big fish will move close to the banks.  We don't even have to wade.  A technical cast w an iris caddis dropped about two feet upstream of a cruising brown and a few seconds later as it drifts overhead...the reel starts singing.  The moral to this story, the best time for the big fish is in the last moments that we can actually see to fish.  Some evenings we go home with great tales.  Others are a long walk back to the car while talking about how we are going to fool them on the next night.  But we know that if we are going to fish for big fish...those late evenings in mid July are prime.  And so it is with many Nino winters...

 

[jaxjagman]

45 minutes ago, Carvers Gap said:

Great comparison graphic.  Gonna call that GEFS MJO "A Header" because it is erasing the header due to being so anomalous!!!  If that Header verifies, we are likely in business...though I don't like the MJO heading for the COD.  If I remember correctly, that pattern ended winter last winter...but it also seemed to precede the strat split.  Now, I am NOT calling for the end of winter.  Though a wall-to-wall cold winter is probably not in the cards anymore either.  That said, if/when the strat split occurs, then we will have a better idea of where this goes.  Just no good bets on my part as those things sort of have random affects...but many times they reset the pattern.  I give that split about 14-16 days before it begins effecting things at this latitude(bout the third week in January).  If we can get last year's blocking this year(about five weeks earlier than last year), then things might get interesting...even very interesting.  As Sutherland noted, the Long Paddock site now has the SOI negative at -3.32.  That is a significant change.  Its positive nature has likely been symptomatic of lingering Nina atmospheric conditions.  IF it stays negative, that likely means the Nino has FINALLY taken over, though all of this wet weather already says that it has.  And remember, my memories of El Nino winters are of cold rains w highs in the upper 40s/low 50s w lows barely above freezing for large portions of winter.  But there have been some notably good Nino winters.  Best case scenario is that that the GEFS goes into phase 7 at high amplitude and takes the tour of the cold phases, crashes into the COD, and strat split affects take over w Greenland blocking.  Worst case scenario is the Euro MJO is correct which means that it goes into the COD before it gets cold, it cycles back into the warm phases, the strat split doesn't happen, and we go warm until early to mid Feb.  If forced right now, I would just blend the two scenarios...GEFS is half right w the MJO as the Euro is too weak and too quick into the COD but the verification is a weak passage through at least some cold phases, a  non-textbook strat split, and a muted warm spell during prime snow climo of mid January, and finally, February living up to Nino climatology with being cold and snowy.  Again, these types of winters require so much patience.  In some cases, Nino winters don't even begin until about the time folks start getting spring fever!  

So, no changes on my overall seasonal ideas...I compare these scenarios to fishing the Madison out West around $3 Bridge.  We get to the river at around 6:30 or 7:00 in the evening.  The caddis(insects) are flying around in the sage just above us.  We plop down on the bank while looking for heads to rise.  We are not in a hurry.  Many folks have already loaded up and gone home, but this stretch of river holds a secret for those patient enough to wait.  If we get lucky, we net an early fish.  Those are often rainbows.  Then we wait, and we wait, and we wait.  When it is almost dark and the air has cooled, the caddis come down to the water to lay their eggs.  We position ourselves so that we are looking directly into the glare of the moonlight or fading sunlight or from the quickly dimming blue overhead reflecting off the dark water.  Then, a stealthy head pokes out of the water and starts sipping caddis off the top.  We may only land one or two fish, usually browns, but they will likely be nice fish.  The micro-currents create all kinds of un-natural drag...but on good evenings things can come together.  The big fish will move close to the banks.  We don't even have to wade.  A technical cast w an iris caddis dropped about two feet upstream of a cruising brown and a few seconds later as it drifts overhead...the reel starts singing.  The moral to this story, the best time for the big fish is in the last moments that we can actually see to fish.  Some evenings we go home with great tales.  Others are a long walk back to the car while talking about how we are going to fool them on the next night.  But we know that if we are going to fish for big fish...those late evenings in mid July are prime.  And so it is with many Nino winters...

r

Problem with this winter is the Euro shows a split day 10 now but both daughters are weak looking and even the weaker one is in NA,guess we'll see how it plays out ,definite split @ 10hp tonight and almost 20,but it's later than what's been hinting at.now 1-5-19