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December/January 2019/20 Winter Speculation Thread


AMZ8990
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14 minutes ago, weathertree4u said:

There is some really cold air upstream. I recall January 1985 how warm it was and then that arctic front came through drpping 6" of snow that everyone said wouldn't stick then I've box for three days

Yes, there is.  I came buy to post about how I actually like the wonky looking 12z GFS.  Big takeaway...EPO ridge.  Rest of the run is all over the place as it leaves a piece of energy in the SW.  The GFS has been advertising for several days some fairly cold air.  The Euro is not on board as much with that...but the EPS is actually better long range.    Looks to me like a pattern that reloads cold in the front range in MT and just keeps sending it SE.  With the active storm system that we have,  any significantly cold and sizable air mass would likely intersect with the active STJ.   Now, I have no idea how long that will hold in place...but it is certainly better than the big ridge.  Reminds me a lot of November when I look at it.  Very warm pattern that takes about 1-2 weeks to step down into a very cold pattern.  Does it verify?  Million dollar question.

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12z GEFS still holding strong with(what so far) an outlier solution of an eastern ridge.  The 12z GFS(different core and newer) is about night and day different.  So something to keep an eye on.  Even on the GEFS looks like the cold air is pressing, but the SER has not budge on that model.  More updates to come regarding ensembles and the Euro run.  Feel free to chime in...

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I know this doesn’t directly impact many people on this forum, but the 12z Euro is showing what would likely be a MAJOR mountain wave event this weekend for East TN.  Details can change between now and then, but that looks like a very high end event currently.

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39 minutes ago, Math/Met said:

I know this doesn’t directly impact many people on this forum, but the 12z Euro is showing what would likely be a MAJOR mountain wave event this weekend for East TN.  Details can change between now and then, but that looks like a very high end event currently.

I was just looking at that and wondered if you were on top of it.... lol

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12z GEFS still holding strong with(what so far) an outlier solution of an eastern ridge.  The 12z GFS(different core and newer) is about night and day different.  So something to keep an eye on.  Even on the GEFS looks like the cold air is pressing, but the SER has not budge on that model.  More updates to come regarding ensembles and the Euro run.  Feel free to chime in...
With the look that keeps showing (very shallow cold air bleeding east) and the active STJ..think the sign is starting to point toward a major ice event in the Eastern US (vs snow). Very shallow cold is typically under modeled in progression at long range (especially as it bleeds into OK/TX/AR region) historically, similar to how modeling typically over scours it in CAD areas.

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21 minutes ago, TellicoWx said:

With the look that keeps showing (very shallow cold air bleeding east) and the active STJ..think the sign is starting to point toward a major ice event in the Eastern US (vs snow). Very shallow cold is typically under modeled in progression at long range (especially as it bleeds into OK/TX/AR region) historically, similar to how modeling typically over scours it in CAD areas.

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The 12z EPS like the 12z GFS(operational) is wanting to belly the ridge into the nation's mid-section.  And like the GFS, one has to look at surface temps in order to get the entire story.  If the ridging is week...it is cold to very cold underneath.  When the EPS has mean surface 2m temps cold in the d10-15 those have been verifying quite cold.  I generally have to use 850 temps to balance the 2m temp bias to warm.  Looks like the trend is to continue to allow for an Aleutian' trough and slightly more ridging into the nation's mid-section which eventually backs into a weak trough.  What today's run tells me is that this is not settled - this meaning the shake-up.  If I was a betting man, I would bet on a stout western ridge and an Aleutian's low.  And yes, very strong signal for multiple over-running events at various latitudes in the lower 48.  Until this gets worked out, tough to know where.  The 12z Euro now has the cold shot around Jan16/17.  Oddly, maybe very oddly, the EPS as en ensemble and GFS as an operational is working as my preference.  They have been leading the way with their respective model groups.  The odd washed out crazy look on the 12z GFS...pretty much what the EPS looked like as well.  Modeling is a mess which is a very good sign of a significant hemispheric circulation pattern change.

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Have seen some quality chatter on various forums(mainly MA) regarding conflicting signals of the PV tightening on the EPS and splitting on the GFS.  We don't want the PV to tighten up per the EPS any more than it is.  We want it displaced per the GFS preferably into eastern NA.  Some of that accounts for variations being seen.  I highly doubt that we are done with the wild wx model solutions.  Probably just the beginning.  Still, I think a very big shake-up is coming.  I welcome that because the big ridge in the East was not going to get it done.  Kind of like you get a bad hand in poker.  Fold and take your losses.  Then, get a new hand dealt and hope it is better.  Pretty much right where we are.  The upcoming hand is about as bad as it gets.  Nothing wrong with getting a new hand.  But....this is what makes this fun.   We get to try to work a new pattern instead of the mega-torch that we will see.  

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18z is a textbook transition.  Right speed but slower than previous runs.  But the result of energy being held back is that the ensuing eastern trough digs deeper.  The model solutions where pieces of the trough are spit out a little at a time results in a mess.  Looks to me like the ridge is going to roll forward in the Pacific.  If so, we want enough energy held back to dig the ensuing trough.  Just another wild run.  When 18z comes around, pretty much pop the popcorn.

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I agree that this setup (as modeled) looks like it has overrunning potential all over it.  Depending on where the boundary sets up, I like seeing a SW flow on occasion.  If the boundary is far enough to the south, this area can see a good snowfall.  More times than not, it seems to be a fence straddling situation and locally we’re on the “wet” instead of “white” end.

Regardless, I like seeing these positive changes on most guidance.  I had pretty much written January off but if we can squeeze a week to a week 1/2 of a decent pattern at the end of the month, I would consider it a win.  A flip back to crappy can certainly happen so I’ll refrain from getting excited just yet... 

 

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Of note the 0z EPS pulls BN heights northward and puts a ridge in the West with an unsettled pattern over the East.  

The 6z GEFS finally moved towards the EPS solutions.  

Overall, still a nice cold signal from Jan 17-21.  After that, still a shakeup expected.  Does the cold lift out and get replaced with a zonal look or does the cold stay in NA and reload the eastern trough?  Does the PV split as hinted at by American modeling?  Before anyone scoffs at the American model at range...the GFS for whatever reason has a pretty good ability to depict TPV splits.  

 

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1 hour ago, Carvers Gap said:

MJO continues to improve with it becoming more apparent that there will no be a quick loop back into the warm phases.  Options include going into the COD or heading into phases 7/8.  Both are not bad.  

Latest run of GFS providing yet another different solution for the long range 

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1 hour ago, weathertree4u said:

Latest run of GFS providing yet another different solution for the long range 

Yeah, for sure.  I think it is pay me now or pay me later.  If a piece of that trough kicks East, we get the first true cold front of January.  If it holds back, the entire thing is going to come out.  The 12z GFS certainly had plenty of blocking and troughs in the correct places.  The SER really wants to hang on in modeling.  That is something we will have to watch.  I strongly suspect it gets beaten down over time.  Looks like some form of an EPO ridge on most modeling with varying "opinions on the rest NA in regards to blocking.  Indeed, the 12z GFS basically flipped all of that from 6z but with mid-latitudess staying similar.   All of this bouncing around lends itself to a substantial stake-up just after mid-month.  The one thing that many models are showing is a stalled frontal boundary over the Upper South and/or Ohio Valley.  Have to watch those with big highs in place.  That would likely be my second favorite setup for winter storms.  Plenty to look at...and some uncertainty as well.  But hey, when is the weather ever a certainty?  I hold cautious optimism that winter is going to return.  If it weren't for last year's head fake, I would be pretty excited.  For now, I tread lightly!   

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11 minutes ago, Carvers Gap said:

Yeah, for sure.  I think it is pay me now or pay me later.  If a piece of that trough kicks East, we get the first true cold front of January.  If it holds back, the entire thing is going to come out.  The 12z GFS certainly had plenty of blocking and troughs in the correct places.  The SER really wants to hang on in modeling.  That is something we will have to watch.  I strongly suspect it gets beaten down over time.  Looks like some form of an EPO ridge on most modeling with varying "opinions on the rest NA in regards to blocking.  Indeed, the 12z GFS basically flipped all of that from 6z but with mid-latitudess staying similar.   All of this bouncing around lends itself to a substantial stake-up just after mid-month.  The one thing that many models are showing is a stalled frontal boundary over the Upper South and/or Ohio Valley.  Have to watch those with big highs in place.  That would likely be my second favorite setup for winter storms.  Plenty to look at...and some uncertainty as well.  But hey, when is the weather ever a certainty?  I hold cautious optimism that winter is going to return.  If it weren't for last year's head fake, I would be pretty excited.  For now, I tread lightly!   

Exactly, was a heck of a head fake last year! 

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59 minutes ago, weathertree4u said:

Exactly, was a heck of a head fake last year! 

Another flashback...the PV appears to be split late in the run and working its way up.  The last two PV splits have been from the strat down.   You can just about take it to the bank that when we get these monster ridges in winter alone the EC...it is going to disrupt the PV(even if modeling doesn't show it at first).    So, the reason that the higher latitudes are all over the place on different runs is probably due to some "goings on" with the PV being disrupted.  

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Pretty happy to see the Euro climbing inside 10 days with this. Also good news on the MJO on both the Euro and GEFS. If we can get the pattern to flip in the Jan 15th to February 15th window we should be in business. Big winter events keep showing up in parts of the forum area, usually in these situations the western areas see it first.  

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1 hour ago, Holston_River_Rambler said:

@Carvers Gap

Sorry, been out this PM, hadn't even had a chance to look at it and just logged in.

Here you go. Not sure why it blinks a little at the end, but weathermodels has been acting up lately. 

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Thanks, Holston.  Nice ridge out West.   Cold coming straight off the pole.  I would not be surprised if this evolves similarly to November where we get the Pacific to cooperate and then the NAO kicks in for a a week or two to close that pattern.  It has been hinted at...but it wouldn't take much for AN heights to sneak into Greenland in that pattern.  Would not surprise me to see the base of that trough retrograde west a bit.  That Scandinavian Ridge kind of tipped its hand to blocking being re-establlished or relocated.

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