Fall Speculation 2018

[Carvers Gap]

Just looked at the slp placements on the 12z EPS.  Not sure that this is sorted out yet....  Definitely tough to get it to snow in the valleys at this time of year, but again, it does happen on rare occasions.  Compared to yesterday, it does appear to have more slp solutions SE of the the Apps w less energy up the west.  Now, to me it does have some semblance of a handoff of energy which has been very common recently during many winters.  Its snowfall maps are slightly more SE w Northwest and West Tennessee seeing accumulations on the individual maps of the ensemble....and the very tops of the Smokies.  I am pulling for the GFS due to my location in the valley.  Not sure what bias is in play with each model at this time of year.  I tend to lean Euro when it shows a cutter, but there are some low road solutions on the EPS as well.  Overall, probably need to see some more agreement before I buy cutter or low-road solutions.  

[tnweathernut]

11 minutes ago, Carvers Gap said:

Just looked at the slp placements on the 12z EPS.  Not sure that this is sorted out yet....  Definitely tough to get it to snow in the valleys at this time of year, but again, it does happen on rare occasions.  Compared to yesterday, it does appear to have more slp solutions SE of the the Apps w less energy up the west.  Now, to me it does have some semblance of a handoff of energy which has been very common recently during many winters.  Its snowfall maps are slightly more SE w Northwest and West Tennessee seeing accumulations on the individual maps of the ensemble....and the very tops of the Smokies.  I am pulling for the GFS due to my location in the valley.  Not sure what bias is in play with each model at this time of year.  I tend to lean Euro when it shows a cutter, but there are some low road solutions on the EPS as well.  Overall, probably need to see some more agreement before I buy cutter or low-road solutions.  

Any transfer of energy with a piece heading into the southern apps (or there abouts) would be the kiss of death for east TN, really probably anyone this time of year.

[Carvers Gap]

5 minutes ago, tnweathernut said:

Any transfer of energy with a piece heading into the southern apps (or there abouts) would be the kiss of death for east TN, really probably anyone this time of year.

No doubt, especially at this time of year w no cold to hold the warm nose at bay.  Yeah, we need the entire slp to slide by w none of it coming west.  Plenty of solutions out there at the moment.  The biggest thing, as Jeff mentioned above, is will the cold air get here in time even if the track is perfect(for E TN folks...perfect is a relative term depending on locals)?  

[Windspeed]

12z ECMWF did crush SWVA and the I-81/I-77 interchange corridor. Pretty much the entire upper Northeast TN Valley Watershed at and above 2,000 ft, and all points North and East from Abingdon had great returns.

[BlunderStorm]

22 minutes ago, Windspeed said:

12z ECMWF did crush SWVA and the I-81/I-77 interchange corridor. Pretty much the entire extreme northeast TN Valley Watershed above 2,000 ft, and all points North and East from Abingdon and above 2000 ft had great returns.

Yeah I'd be crushed. With how heavy and wet that snow would be I could see power being knocked out for a lot of folks up this way.

[Daniel Boone]

Let's not forget, the Euro does have a warm bias. Even though it is the best medium range model, it does have it's flaws. Not only the warm bias but, also it not being precise in terrain detail in our area.  I.e; the higher terrain along the ky/va border. Much of Buchanan County is not within the higher elevated high knob landform like northern Lee , Wise and Russel Counties are. The snow map clearly shows the Model sees it as it is.

[John1122]

While verbatim the outcome changed some on the 0z GFS vs the 12z today. The track/intensity/hp to the northwest stayed virtually the same on the GFS. Gonna be borderline for a decent miller A storm or just a perfect track wasted if the GFS comes to pass. If it were December the 15th we'd be rocking with that path statewide or close to it.

[BlunderStorm]

1 hour ago, John1122 said:

While verbatim the outcome changed some on the 0z GFS vs the 12z today. The track/intensity/hp to the northwest stayed virtually the same on the GFS. Gonna be borderline for a decent miller A storm or just a perfect track wasted if the GFS comes to pass. If it were December the 15th we'd be rocking with that path statewide or close to it.

It's looking like an uphill battle with the "supposed" changeover being during mid-day in a November for the eastern valley. We just need the cold air in place a little quicker and I guess that would imply either a better positioned/stronger high pressure west of us or the system arriving a little later. If we had the cold 6 hours earlier at dawn on Tuesday I would feel a lot better with what the GFS is showing. As for other models for the 0z ICON the cold air simply never reaches our sub-forum. The 0z Canadian presents a similar scenario to the most recent GFS except with maybe more potential for snow in west Tennessee. The 0z FV3 is pretty much in line the GFS and Canadian as well. Will see what the euro brings to the table but I have a sinking feeling it's going to be like the ICON with how it ran 12z as an Apps runner.

[Windspeed]

Still way early in modeling but if I had to anchor a call, I'd place confidence in higher range eastern Cumberland Plateau and SWVA for 3+ in. accumulations. Everything below 2k ft needs better modeling support at this point. But again, it's early.

[AMZ8990]

 Gfs trying to double down with this mornings run, Euro is still warm until the precip moves out.  Starting to see some similarities between the gfs and cmc the last few runs but I’ll believe it once I see it.  Models are definitely hinting at something though, today and tomorrows runs outta start to sort this thing out as we approach Monday. Nice to see a few models in somewhat of an agreement though.  It would be nice if the euro would join the party though.  Hope everybody has a blessed Friday,  be safe out in the rain today!

AMZ

[Carvers Gap]

Short range:  Looks like great discussion by everyone...only thing I would add is that the 6z GFS looks like it trended a tad northwest.  I have not looked at the EPS yet.  It may be that the slp is just too weak.  If it is stronger AND along the coast, it will pull in cold air more quickly.  That said, a stronger storm might be more northwest anyway.  With that slp not being "wound-up" it needs the cold to be crashing in more quickly than depicted.   

Way into the LR:  The Euro Weeklies did hold serve with warm weather from Thanksgiving to Christmas with some cold interrupting the pattern.  Though, the 42 day map is still overall cold due to the strong cold coming during the next couple of weeks.  I am not sure at this point that I totally buy-in to the warm for that length of time as depicted by that run - it certainly would be within climo though.  Why?  Similar to last winter(eh...maybe the winter before...can't remember) there is good blocking over AK and Greenland, and the model drags its heels in the West and leaves the cold there.  Eventually the mid-latitude trough retrogrades into AK.  I generally think a cold AK teleconnects to a warm forum area over long periods of time.  The model may be correct.  It seemed a bit wonky and maybe its teleconnections are off a bit...but it does fit climatology.  The good thing is that the model does try to break down the pattern around Christmas...It is not a total washout by any means either.  There is some cold that slides eastward.  Still, I know many good mets who wait until mid-Nov or a bit later to make their final call for winter.  Why?  It is not unusual for LR models to completely miss the December pattern at this range.  So, we will really need to wait one or two weeks before giving strong credence to December patterns.  We have seen predicted cold patterns be warm and predicted warm patterns be cold at this range, especially around this time of year.

[jaxjagman]

I see the cold biased CMC hasn't change any.9 degrees around Nashville Wed morn.Though all the models did trend slightly colder.Euro is now 21 while the GFS is 15.

[nrgjeff]

Carvers is very on-point about the Euro weeklies above. I have little to add to the surface weather outcomes. Here is my take on the 500 mb clusters, and I will lean cool.

Thanksgiving week looks mild from the Plains into the Mid South, and perhaps the Valley. However by week 3 (after Thanksgiving) the AK ridge tries again, might be other blocking. If so, it is a short warm interlude for Thanksgiving. Surface is not too cold week 3, but 500 mb is not that warm either.

Week 4-6 composites are a mess. Drilling down the clusters helps a little. Majority clusters do not show blocking. However large minority clusters do have blocking each week, sometimes multiple blocks. I will tell you the surface weather if you can tell me the stock market, lol! However I will go changable. 

Bottom line: I like variable and agree with Carvers. 

PS. Don't take my silence about snow I-40 north as a bust. Figure it will at least Plateau and Mountains. However I don't have a prayer in Chatty. Good luck!

[Carvers Gap]

Just glancing at the 12z suite as it rolls-in....I still like northwest TN(including southwest KY) for best chances to see some snowfall w maybe a dusting to a couple of inches.  I don't think anyone is out of it at this point, but it seems the issue is with getting cold air into the equation.  Pure speculation on my part...maybe the first system doesn't drive far enough south/east and leaves some work to do for the system that we are watching.  The Ohio river region is looking fairly good as well.  Now, I don't think anything is written in stone.  I don't buy the Canadian w the backend thump for NE TN.  That just rarely works out with that set-up IMBY.  The mountains could see something which seems reasonable.  We will see what the 12z Euro has to say in a few hours...

[John1122]

Looks like the GFS is slowly moving NW with it's track. As I mentioned yesterday or the day before, the Euro track seems more likely and the GFS is slowly heading that way. 

[John1122]

Euro says the ground may get white in a few areas, far NW Tn being the most likely place it happens. That same area gets buried by the experimental GFS. Looks like classic cold chasing rain, models usually over do that significantly, so for most of us, hope to see some flakes. For our W/NW areas, hopefully you actually get smacked with a nice snowfall.

[AMZ8990]

17 minutes ago, John1122 said:

Euro says the ground may get white in a few areas, far NW Tn being the most likely place it happens. That same area gets buried by the experimental GFS. Looks like classic cold chasing rain, models usually over do that significantly, so for most of us, hope to see some flakes. For our W/NW areas, hopefully you actually get smacked with a nice snowfall.

Yeah north west Tennessee tends to always be in the best position for snow with just about any system.  Maybe just maybe I can get in on the action if northwest tn is in in play.  Your right though, a lot of discrepancies with when the freezing line pushes threw and where the precip is once that happens.  We might get close to a record low next week too, I’ll have to check the analogs and see what the record is currently in my area and around the state!

[Holston_River_Rambler]

Yeah, except for NW areas John mentions, starting to look like it's a done deal for the first wave. Even with some of the more SE tracks, it's still a very cold rain outside of those areas. 

I'm grabbing at straws (why not it's just November?), but I'm still kinda sorta interested in a possible secondary wave, from a bit of energy that cuts off over TX or N. Mexico.  It's there on most models, but most string it out and kick it along or bury it.  Ifs and buts....... I know, I know .   The 12z ICON has it (I don't think the ICON has ever been right when it's on it's own), but the solution shown by the ICON today, was what the 12z UKMET and EURO had yesterday. The 12z GFS sorta kinda tries to do something similar, but everything is too positively tilted and kicked along by more northern stream energy. The UK and EURO still have it today, but it finally kicks out too little too late. A few of the EPS members have it (member 43 is a monster cut off).  Three or maybe four GEFS members have it too. Not in any way trying to get anyone's hope up about something that a handful of ensemble members have, but I think something like this is still on the table.  It seems like a delicate and subtle thing that may not be resolved until much closer and I'm just interested in seeing if it can happen.  

 

[John1122]

Late in it's run, but the NAM is onboard with the GFS in nailing the NW portion of the state. Dyersburg looks to be in a nice spot to get a few inches of snow if it verifies. Timing will be favorable as will 850s. Rates would help overcome ground temps. The rest of us get the absolute misery of both a missed opportunity and rain with temps in 35-40 range. 

Meanwhile, much like last year and the deep south snows, this one has the potential to put areas of Northern Texas and South/Central Arkansas 2-5 times over their normal yearly snowfall totals before November is over if the American models are to be believed. 

The Euro is much more conservative and blanks these areas.

[John1122]

Euro is steadfast in saying very little to nothing for our forum area. GFS and GEM both came in with lessened amounts. I expect the NAM will follow suit soon enough. The perfect HP/LP set up from a few days ago has disappeared. The HP that was coming down into the midwest is no where to be found. That allows the storm to track further north and it's not there to deliver enough cold. If that indeed comes to pass, the Euro will take an early 1-0 lead on the GFS . Nice to have something to track this time of year, hopefully it's more a normal thing this year than the last two.

[Holston_River_Rambler]

Majority of EPS members still show a piece of the energy holding back and not passing our latitude until next Thursday-Friday.  Some show something like the operational, a few others try to make deep cut off west of us. Depending on individual track, I'd say about 1/3 - 1/2 of the EPS members give parts of our area a little (as in 1-3 if you are lucky) snow.  The GFS says no on the secondary system, but some uncertainty evident on the GEFS spaghetti plots (image below).  Even the NAM is trying to be a little bullish with the energy at the end of its run, closing off a 528 height line over N. TX. Sure it's the NAM and at the end of its run, but this sort of a solution has some support. 

Most of the solutions that show this coming out, pop a low too far east to bring any precip. into our area.  Even my hobby horse from yesterday the ICON is waaayyyy south and east at 0z.     But......how has the first wave trended over the past few days? 

Trying to understand the Typhoon Tip post cited by Carvers earlier and if I understand it correctly, this sort of shortwave might have a better chance at amplification since the geopotential heights associated with it are higher at a lower latitude, so there isn't as much gradient. I could be entirely misunderstanding that. Apologies if so. 

I think (if I had to give a percentage at this time: 75% chance) there will be a low form in the Gulf late next week and it will move NNE. Where this happens and how it moves remain to be seen, but if it happens at all, I think a NW trend will be part of it. Fall SE ridge seems to be stronger than models are seeing from distance.  I also think unless this low cuts off and cranks up, any snow will be elevation based and nocturnal. I have to be in Hot Springs, NC all day next Friday, so I have vested interest.  

[John1122]

The Canadian pops the 2nd wave and rides it up the coast, but it's too warm to snow. The 850 line is hanging out in Southern Canada so it's upper 30s and raining again.

It enhances the back side of wave one more and drops 1-2 inches from 40 north from Crossville to Cocke Co and points north.

[John1122]

The Euro also has system #2 now, ice in the Carolinas right now, rain here. 

[Carvers Gap]

Regarding the 12z EPS which is not infallible BTW as we have seen recently.  I will share the 500 maps which show the zonal pattern developing around day 8(it is moving forward consistently in time)...the corresponding map is a 5 day map for days 7-12.  It will take a few days for Pacific air to fill the new pattern.  I will also share the 850 maps for days 10-15 - when the Pacific air moves into NA w likely chinook influences.    Now, again, I am most interested in what happens after the zonal time frame(I really have no interest in warm time frames unless it is a means to an end), because that is really when climatology begins to support winter weather, ie the window opens for winter.  The models definitely jumped the gun regarding the zonal pattern, just no denying that.  So now we are down to a battle of weeks 1/4 vs 2/3 in terms of November being BN.  Like John said in the winter spec thread, TRI might be tough to get BN, but other cities in the forum will have a good shot at below normal temps for the month.  And again, some positives to take away from this cold snap...several models missed the amplification and duration - for starters it was colder and longer in duration than the Euro Weeklies foresaw.  So, we will need to be careful going forward...if the Euro Weeklies show any BN heights over the SE during the 4-6 week range, those departures from normal might be a clue to a great outbreak of colder air.  But overall, the Euro Weeklies did fairly well once they sorted through weeks two and three.  It is not unusual of for any model to end a period of cold and blocking too early.  Now, this is likely my last post on the zonal pattern which is likely to develop simply.  Why?  I  am beating a dead horse at this point.  LOL.  So, what I want to concentrate on is where this pattern goes after the zonal timeframe(timing and blocking set-up).  Just seems that the ENSO state is going to at some point plop that trough in the SE and then be very difficult to move.   That is the transition that I am looking for...  

As a little aside, I noticed that isotherm mentioned that there were very few analog years for this upcoming winter set-up.  I concur.  But I do think we can use the November pattern to provide clues, and I like what I see so far.  What "I hope" to see is the ridge roll forward, a trough drop into the West, heights build over AK, and then the trough move into the SE.  You can sort of see that if you roll that bottom map forward in time...not sure if it wants to spend some time in the West first.

[Carvers Gap]

Regarding the last few days of November and early December...For those of you who like medium to long-range forecasting, I think the models are well worth you while this AM.  Both the 0z EPS and GEFS are showing some hints of blocking very late in their runs.  The EPS is slower and the GEFS is likely a bit fast and a bit too far out there for me to bit yet.  Sometimes the GEFS can also be overly cold, but it can sniff out patterns sometimes when the EPS is too slow to change.  The skinny is that a ridge moving into AK w heights rising over Greenland is a great look.  They have been hinting at this for a couple of days.  Temps on the EPS are much warmer in the d10-15 than the GEFS.  That said, the progression is similar, but slower on the EPS.  We will see how quickly this can move forward in time as it seems everything has been occurring (in real time) more slowly.  I don't want to see a zonal pattern locked-in, because they are a bear to break.  The GEFS would limit any warmth to just 4-5 days while the EPS would probably allow for a week or two.  Maybe a blend of the two would be nice.  Either way, this is where I am interested and have been interested.  Can we get Arctic air into the pattern for December?  Just based on the past couple of days model runs, maybe.  I think isotherm does a great job setting up that potential path.  If I had a choice, I would have the outbreak arrive in mid-December.  Early December climatology is just no conducive in NE TN for snow prior to say Dec. 10th.  It gets better quickly after that.

[Holston_River_Rambler]

Hard to argue with those ensembles.  My question now (if we assume blocking evolves which I am based on what you and others have written) is when does this = our first chance. I remember last winter the blocking seems to benefit areas N and E in the US first and then towards the end of the regime as it starts to break down we get some shots.  Last winter was a very different base state, but the blocking (although SSW driven then) seems to have evolved in a similar E to W across the N. Atlantic. Does the changing QBO hinder or help an E to W progression this year? I have no clue, but thought I'd ask.  

The cold/ pattern seems to be lingering more than expected as we go through time.  Unless I'm misremembering, this coming weekend's cold shot was predicted to be the beginnings of zonal a week or so ago. Not saying pattern won't go zonal at all, but maybe 2 steps froward (current pattern), then 1 step back (zonal), then 2 more forward (blocky). 

It doesn't seem to be taking much for Gulf Lows to form. How does that change all this up?  Do we get a few earlier shots in Dec. or do we have to wait our turn as the block evolves and degrades for even better shots? If I remember the progression last winter, it was around a month from when we first started seeing the blocking appear on models to the first shots we had.  If that is the case mid Dec on, should offer at least a window or two. 

Also, still clutching out a frayed strand of a hope for this cut off upper low this week.  Maybe someone in the forum's western areas gets lucky and gets a quick burst of snow if it rolls overhead. 

[jaxjagman]

South Korea 2M forecast for Dec.,Jan.

[Carvers Gap]

1 hour ago, jaxjagman said:

South Korea 2M forecast for Dec.,Jan.

Great share.   That is textbook weak/moderate El Nino.  I am now more than just a little interested in how December shakes out.  Honestly, we probably ought to hope that it gets warm...because that is likely a good setup for December in the long run.  Just roll that pattern forward a week in my post from yesterday.  Again, I think the American models are likely too fast...the Euro might be too slow.  If we can dodge this warm-up, that likely means that we are entering a base state that is cooler than normal.  In other words,  when in doubt...go BN.  That is quite the opposite of some winters.  Color me cautiously optimistic.  I am probably the last person to hop on the band wagon, but it might be time...give me a couple of more days!  LOL.

[AMZ8990]

31 minutes ago, Carvers Gap said:

Great share.   That is textbook weak/moderate El Nino.  I am now more than just a little interested in how December shakes out.  Honestly, we probably ought to hope that it gets warm...because that is likely a good setup for December in the long run.  Just roll that pattern forward a week in my post from yesterday.  Again, I think the American models are likely too fast...the Euro might be too slow.  If we can dodge this warm-up, that likely means that we are entering a base state that is cooler than normal.  In other words,  when in doubt...go BN.  That is quite the opposite of some winters.  Color me cautiously optimistic.  I am probably the last person to hop on the band wagon, but it might be time...give me a couple of more days!  LOL.

 Go on and hop on the train CG!

[Carvers Gap]

56 minutes ago, AMZ8990 said:

 Go on and hop on the train CG!

I am on the cool winter train(been there a while)...just not on the cold December one - yet.  That said...check this out from the CPC today. Now, I really like winter storms showing up around a dip in the NAO and its following rise.  Now, the forecasting of the NAO has been abysmal recently and that is one positive trend that will be tough to buck.  But that drop would be something else....