December/January 2019/20 Winter Speculation Thread

[Carvers Gap]

Ridge reforms after 300.  Looks like a slightly westwardly displaced -EPO trying to pop.  Modeling is beginning to throw less than consistent looks after d10 instead of a locked-in pattern.  Likely a shake-up upcoming after d10.

[Carvers Gap]

Both the 12z CMC and the GFS look like a very slow retrograde of features in the Atlantic, Pacific, and in North America.  Every time a cold front pushes eastward, the ridge displaces a little further to the west. 

[nrgjeff]

Extended is depressing. However the Upper Plateau and over by the Tri Cities may have a nice Tuesday. Does not look big, but looks like something.

Upper Plateau and TRI, appears the column will cool enough up there thanks to dynamic cooling. Thickness and 850 both get down with QPF after the fall. Snow output is noted on most models, but I still like the thickness QPF method best. It looks good. Maybe only an inch or two (the 2 higher elevations). Daytime is a challenge, but not as much so in January compared to say late Feb.

Meanwhile south of I-40 looks hosed, especially KCHA and southeast Tenn. Oh but we may have some severe fun this weekend. More in that thread after the 12Z Euro.

[Carvers Gap]

12z Euro continues the trend of dislodging the western trough.  How long?  Who knows.  Looks like a shake-up is coming.  Edit:  For those who have not read my previous comments...reference is d10-15.

[Carvers Gap]

Out to 270 on the 12z EPS pretty remarkable weakening of the AN heights over the eastern Pacific.  

[Carvers Gap]

12z EPS has a full latitude trough just after 300.

[Carvers Gap]

The 12z EPS continues its trend of improving the pattern over eastern NA if one likes winter. Weak  -EPO is in place w a trough over much of NA by 318.

[Carvers Gap]

12z GEPS(Canadian) shows quite a bit of improvement with a common theme being a -EPO.  IF these models are correct, the shelf-life of that huge anomaly over the eastern Pacific will be just around 10 days.

[Carvers Gap]

12z EPS is frozen at 318.  Of note the control has a strong -NAO.  Way out there and likely changes, but it is raging on this run.

[John1122]

If we can get that look to maintain and roll forward in time we might be on to something. Until it does, it's hard to believe it or the GFS. 

[Carvers Gap]

Very much agree to watch for the head fake, but I do think the MJO supports at least a relaxation.  If anyone has 318-360 for the EPS, please share how it ends. My source is stalled.  The 12z GEPS and EPS both look very good.  The 12z GEFS looks decent.  The GEFS, with its old core, is not there yet.  The Euro operational actually has heights rising over Greenland near the end of its run.  Pattern "should" be due to end by mid-month so much of this does make sense.  Looks like most of this is rolling forward in time as the changes are beginning to show up around d10.  But legit to question whether the models hold.  Given climatology, the current pattern duration(nearly 6 weeks by that point on modeling), the MJO heading out of warm phases...makes sense for at least a relaxation.  But very good to be seeing changes vs seeing the current look digging in.

[nrgjeff]

Weeklies try to bleed cold south week 3-4 but dang it's ugly. BN heights over the Great Lakes attempt to drive it. However the PNA looks neutral at best; never really goes negative. Some AK and Western Canada AN heights but US West heights are dreadfully BN. Could spit out energy I guess; but, also WAA ahead of each wave.

Figure the SER torch fest will tone down, but not going full tilt cold though. On the optimistic look, it only takes one system to phase right in that choppy pattern noted above.

[Carvers Gap]

The 12z EPS finally completed its run.  Looks like there is a -EPO and maybe part of the ridge peaking into PNA territory.  Mean trough is centered over the eastern Plains with cooler air surging eastward d13-15 w a very weak SER. This morning's run wasn't bad.  This one was better and very similar to the 12z GEPS and 12zGFS.  12z GEFS is out on a limb w the western trough.  Looks to me like a pattern very similar to November "trying" to develop where cold pushes into the front range and then surges eastward.  So, let's see if those trends hold over the next couple of days and even improve.  The good thing is that the big red ball over the eastern Pacific is forecast to weaken substantially.  Ah...bout forgot, the Scandinavian ridge is still present on the EPS.    This has not been a sudden flip on modeling as the trends have been working there way into the medium and long range for several days.  Now, can we get a trough to hold in the East?  TBD.

[Carvers Gap]

Take it with a huge grain, but the EPS control has a massive -NAO right over Greenland d10-15.  I won't hold my breath but worth sharing.

[Carvers Gap]

Looks to me like the Weeklies don't belly the ridge into California.  The 12z EPS does and forces the EPO ridge slightly into PNA territory.  The 12z EPS pushes the ridge further eastward into California where 0z(Weeklies were derived from that run) does not.  Subtle differences, but can make a big difference.  The 0z run would have allowed BN heights to slide west of the Continental Divide...12z run forces it all east.  Big question will be whether the AN heights over the eastern Pacific are gone or just on a brief hiatus.  We definitely want to see the EPO ridge pushing inland as the AN heights right on the tail of the EPO ridge will likely reinforce it wherever it is.  Weeklies imply a window from Jan20-30th.  Could be shorter or could be much longer.  Going to probably be some wild model runs with the shake-up around the 18th.  Looks like a lot of modeling is hinting those changes that will weaken the easter Pac ridge begin around d10.  Going to be a BIG warm-up in the meantime but maybe we can see the end of it now?  Time will tell.

[John1122]

Not a particularly great model but supposedly better in winter than other season, the CFS turns us to winter and then has 3 snow events in the January 22-30th timeframe.

[Carvers Gap]

Of note, we were in a similar position last year expecting a change for the better, and we know how that turned out.  That said, this year we have not had a PV split, the weak Nino/Nada appears to be coupled with the atmosphere, and the MJO is potentially trending into the COD.  Nino winters have fickle end games so proceed with caution.  I don't think anyone can fault us for crying wolf with cold this winter.  We have been banging the drum for warm since early December with the occasional celebration of a non-torch run.  It is worth noting(the MA talked about this today and I mentioned it last week), the snow on the ground in the NW is not like last winter in most places.  They have had snow, but there are places just outside Yellowstone with bare ground at times.  So, they have not had a snowmegeddon like last February - yet.   Maybe they build a glacier over the next ten days.   I mention that because average to below average snowfall in that area is tied to an El Nino pattern.  That said, global snowfall is down a bit in general with the PV at record strength.  The west actually has some negative departures in the northern Rockies.

https://climate.rutgers.edu/snowcover/chart_daily.php?ui_year=2020&ui_day=5&ui_set=2

Other things in our favor are climatology and that we had a cold November.  Climatology is worth a quick discussion.  This is more of a positive La Nada instead of a weak El Nino.  The cold off SA certainly has a Nina characteristic.   So, what climatology are in?  That is up for debate IMHO.  If it is Nino climatology, we should have a cold end to winter.  If it is Nada climatology, those winters are usually meh end-to-end. The cold November is likely in our favor if one buys that the past two cold Novembers are not the result of a warm Pacific basin forcing the pattern to turn cold in November and then subsequently warm as the winter season settles in.  The QBO is now descending and not stalled.  If it can get into negative territory, the downward trajectory combined with negative territory will enhance that index - like double bonus points on a video game.

Things not in our favor.  Does anyone really trust the MJO at this point?  It really shouldn't be heading into warm phases at this time of year during Nino(if we assume this is a weak Nino...again debatable)conditions, but there it goes.  Will it loop back into warm phases and is the relaxation on the modeling just it entering the COD before re-emerging into less favorable phases again?  Climatology is not in our favor if this is in fact a Nada.  The PV needs to be knocked of its spot...right now it is too tight and needs to be jostled around preferably into any eastern trough!  If one adheres to patterns lasting 4-6 weeks, the pattern should at least reshuffle(that doesn't always mean a better pattern) by mid January.  Again, that did not happen last winter.  

As of this writing, the model trend is in our favor.  However, we know that there have seen false alarms all winter and last.   At this latitude those probably won't be the last false alarms.  The real question I have is whether we enter a new pattern dominated by an eastern trough in the means OR if this reverts back to a ridge after 7-10 days.  I don't think we know the answer to that yet.  I lean towards an eastern trough, but it is only a lean.  This is not last winter, and past performance does not equal future results ...but sometimes in the weather past performance sort of does(let's just hope the pattern in November is what is remembered).  Patterns do matter, but the atmosphere doesn't have any memory of last year.  However, the active MJO is a commonality and should be factored.

So today, we are cautiously optimistic which is better than wall-to-wall warmth.  As Bob Chill noted, the EPS is probably the best it has been all winter from d10-15.  That said, will that trend continue as it has for several runs?  

[Holston_River_Rambler]

I haven't looked at tropical convection in  bit, so thought I'd give it peek.

According to the RMMs we are in 4, but I would say that there is more to the convection than the RMMs now:

Western Pac:

Now granted that doesn't look great, but if you subtract that TC over Norther Australia, convection looks pretty scattered out and there's even a few flare ups in the N. Hemisphere, pretty far to the east.

 

IOD region is looking active again too, 

but there are also some flare ups in sub Saharan Africa and I think that correlates to phases 8  and 1. 

According to the JMA OLR plots 

It's having some effect from that region, but is being muted a little by the deep subsidence over India. 

EPS mean really wants to quieten down the Maritime Continent pretty quickly now. Mean OLR of days 10 - 15:

Honestly, I'm kind of surprised it doesn't look worse right now in the MC region, given how some of the MJO forecasts looked. Maybe it gets worse there sooner, but still doesn't look nearly as bad as it did last year. 

[Carvers Gap]

Holston, Mike Ventrice had a 2-3 consecutive tweets about the MJO region earlier today.  They were really good.  

18 GFS looks like it is on its way to eliminating the eastern ridge once again.  Fingers crossed.

[Carvers Gap]

18z GFS again completely erases the eastern ridge.  Run ends with a snowstorm.  Pretty cool.

[Carvers Gap]

Probably a more accurate statement is there is a massive ridge in the West after 300 right were it is cold this week.

[Holston_River_Rambler]

Yeah that was a pretty ending for happy hour! 

[Carvers Gap]

23 minutes ago, Holston_River_Rambler said:

Yeah that was a pretty ending for happy hour! 

That run has been money for about three straight days.  LOL.   The place where it ended at 500 is probably something @John1122 would approve of which is a cooperative Pacific and a big ol' -EPO.  Fingers crossed the trends of the past 48 hours continue.  Good thing is operational models almost have the transitional elements inside of d10.

[Carvers Gap]

18z things that were good.

-EPO:  Check

+PNA:  Check

Aleutian Ridge:  Check

-NAO:  As the emperor in Gladiator would say......

 

[Carvers Gap]

The 18z GEFS is still doesn't agree with the operational.  I suspect them having different cores is the problem.  That said, the eastern ridge is more suppressed than previous runs but still solid.  Might that be the beginning of it moving?  IDK.

[John1122]

The GEFS is currently the outlier among all modeling.  So we have that on our side for now. 

[John1122]

28 minutes ago, Carvers Gap said:

That run has been money for about three straight days.  LOL.   The place where it ended at 500 is probably something @John1122 would approve of which is a cooperative Pacific and a big ol' -EPO.  Fingers crossed the trends of the past 48 hours continue.  Good thing is operational models almost have the transitional elements inside of d10.

All day every day on running with a favorable Pacific. It controls everything up stream for us most of the time. If we want cold air it's not easy to come by unless the Pacific is cooperating somewhere.  I've seen a bad Pacific blow a -NAO/-AO but I've rarely seen a favorable Pacific spoiled by the lack of those drivers.  We had repeat snow and ice storms along with below 0 cold valley wide just a few years ago with nothing but the EPO in our favor.  

[Carvers Gap]

Griteater posted this on Twitter.  

 

[Carvers Gap]

New EMON MJO is out today.  The Euro has been kicking butt and taking names regarding the MJO.  It is not perfect but IMHO its performance has pretty much exceeded any other model.  Looks like COD after this two week trip into the warm phases.  That fits nicely with the EPO ridge becoming a main driver sometime after mid-month.  JB did mention that convection has fired in the western IO which corresponds to phases 1 and 2.  We have been there before with that.  He mentioned that modeled the null phase may be the model splitting the difference between 5/6 and 1/2.  Shakup still apparent on modeling.  Looks like the target date for the first front will be around January 16/17.  That front will likely be muted and be a seasonal front, but there is a chance it is a truly strong cold front.  Quick warm-up after that...and then the eastern ridge is modeled to get beat-up pretty good if not completely removed.  12z EPS looked good last night.  GEFS is SLOWLY coming around...its MJO is an outlier right now and is likely causing that model to be an outlier.  Meanwhile, the operational GFS bounces between the trough coming east to just a jumble of AN and BN heights scattered randomly throughout the lower 48.  Again, going to be lots of model variations if the shakeup is real.  If the EPS holds through tomorrow afternoon, my confidence will really grow.  

[weathertree4u]

1 hour ago, Carvers Gap said:

New EMON MJO is out today.  The Euro has been kicking butt and taking names regarding the MJO.  It is not perfect but IMHO its performance has pretty much exceeded any other model.  Looks like COD after this two week trip into the warm phases.  That fits nicely with the EPO ridge becoming a main driver sometime after mid-month.  JB did mention that convection has fired in the western IO which corresponds to phases 1 and 2.  We have been there before with that.  He mentioned that modeled the null phase may be the model splitting the difference between 5/6 and 1/2.  Shakup still apparent on modeling.  Looks like the target date for the first front will be around January 16/17.  That front will likely be muted and be a seasonal front, but there is a chance it is a truly strong cold front.  Quick warm-up after that...and then the eastern ridge is modeled to get beat-up pretty good if not completely removed.  12z EPS looked good last night.  GEFS is SLOWLY coming around...its MJO is an outlier right now and is likely causing that model to be an outlier.  Meanwhile, the operational GFS bounces between the trough coming east to just a jumble of AN and BN heights scattered randomly throughout the lower 48.  Again, going to be lots of model variations if the shakeup is real.  If the EPS holds through tomorrow afternoon, my confidence will really grow.  

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