Fall Speculation 2018

[Carvers Gap]

Looks like the operational runs today are all over the place today. Anyone willing to lock down the 12z GFS and call it a November?  Anyway, going to be tough for operationals as the back-and-forth of the coming month will test their rigor.  One rule of thumb that I forget every season, if BN air enters the equation...models can get jumpy during late fall and winter.  That may need to be considered.  So, outside of the ensembles...we may be entering a time where we are going to see a lot of bouncing around.

[nrgjeff]

Weeklies, Ensembles and Ops are of course conflicted. Blocking seems to be persistent, or at least present a majority of the days. At the same time, global wind MJO and Kelvin waves want to promote zonal flow. That's what I see at the broadest level. Results indeed should be back and fourth where we live.

Thank you all for the foliage reports! Chattanooga visibility improved today. In the last 48 hours things have improved markedly. Lookout Mountain and Signal Mountain look fairly colorful. No pictures; still cloudy. However, this weekend it is certainly time to hike! Everybody enjoy weekend leaf viewing.

[Carvers Gap]

Speaking of the EPS...I thought we would watch the time frame that was discussed above, November 12-17.  The zonal period is still on the model, but is getting held in the d10-15 time frame.  Now, how many times have we seen cold temps held in that time frame?  Often.  Maybe the models jumped the gun a bit w the zonal flow, maybe it is a false feature.  Maybe they are eroding the early month trough a bit too quickly.  However, one would think w a low over AK and a +NAO...that does not correlate w cold over the SE, but indeed that is exactly what is there.  What "should" happen with those features at higher latitudes is that low should lift out and Pacific air should enter the US for a time.  Right now, the timeframe that I referenced above now shows a mean trough.  However, there is still a noticeable zonal pattern over NA in the d10-15 time frame set for November 14-19th.   Do I think we enter a period of zonal flow mid-month?  I still do.  That makes since given that Greenland and AK are not ideal. I should also note that temps during the 0z d10-15 do not correspond to the 500 pattern.  

As for the 6z GEFS, it is similar but about two days slower than the 0z Euro.  The trough lifts out.  However, the interesting thing is that it has a more favorable western pattern w AN heights over AK.  Both models depict a very positive NAO.

Also, just glancing at the stratosphere...the upper levels of the stratosphere over the pole look very stable and tight which is not uncommon at this time of year...I think.  The only reason that I mentioned that is that(as mentioned above) there has been some chatter about it being the zonal pattern preceding the vortex being displaced.

The length of the potential zonal pattern and what happens immediately after is of interest to me.  Though I do not have an early start to winter in my thinking, I certainly hope those forecasts are right!  So, I hope we see the back/forth pattern continue into December.

Additionally, plenty of close calls on the 6z GFS...might be worth a look for you all.  That is the view from my end of things this AM...hope everyone has a great Sunday. 

Also, KEEP AN EYE ON JAX'S SEVERE THREAD.  That potential arrives tomorrow(in some places overnight tomorrow).

[Carvers Gap]

The models since this AM do allow space and temps for an early winter storm to form east of the MS during the next couple of weeks.  Climatology limits our chances...but worth mentioning since the EPS has a handful of individuals that produce a sizable storm for the interior SE.  Just throwing it out there as something to watch.  The two possible tracks are over the Ohio River Valley or one that takes the low road.   

I am still thinking of a pretty considerable warm-up after this significant cold shot which will last for at least 10-12 days...and this is almost winter time cold that is depicted on the operational runs.  The best case scenario is that the warm-up is just a mirage...but again, it makes sense given that blocking is not optimal.  However, plenty to talk about in the short range w the severe threat tomorrow night(Jax already has a great thread posted) and a decent bout of cold weather on the horizon as well.  Couple of more days of very warm temps and then a big cool down...

Also, seeing several pics of light accumulating snowfall on Roan Mountain from Friday night and on the mountain tops near Boone.  Looked like a heavy dusting up or maybe even an inch or two based on pics from Carvers Gap and some folks that headed to Banner Elk.  So, the first snows at elevation have been observed.

[nrgjeff]

EPS certainly turned sharply colder, along with the GFS and even stubborn CFS. Seems the upper pattern prevailed. A mild period around Thanksgiving would not surprise me. However I think the CFS is still too warm. Prefer the Euro ECMWF weeklies.

Warmer CFS may be rushing the MJO into warmer phases; then, keeping it there. Euro does better with most phases of the MJO, including these. I prefer the slower return to mild and a shorter mild period at that.

With the clouds forecast the rest of this week, esp brutal at time change, I am already not sure if I like El Nino. Keep reminding me the winter pattern may be good.

[John1122]

Looking more and more like the first lower elevation flakes of the season are going to be possible somewhere over the valley early next week. Clarksville to Nashville and points East look most likely right now, to see snow showers. The Euro and GFS are putting out .5-1.5 on the Plateau/SEKy/SWVA with 1-3+ inches in the mountains.

[John1122]

Euro snowfall map for next week. Obviously still a ways out and the accumulation is a crapshoot at best. But 43 of 50 members of the EPS at 00z had some form of dusting or more for the various parts of the valley. Most were clustered like this snowfall map but some were more West Tennessee based, of member mauled NW Tn up through SWKY.

 

 

More important to me is the significant cold being modeled. My cold November stance is well noted and this cold snap is just what I was hoping for. Hopefully it comes to pass, even though I'm going on vacation to SW Florida next week and temps when I arrive there are forecast to be 15-20 degrees below normal. The normals where I'm going is 83/64 so probably looking at 70/50ish.

[Carvers Gap]

17 minutes ago, John1122 said:

Euro snowfall map for next week. Obviously still a ways out and the accumulation is a crapshoot at best. But 43 of 50 members of the EPS at 00z had some form of dusting or more for the various parts of the valley. Most were clustered like this snowfall map but some were more West Tennessee based, of member mauled NW Tn up through SWKY.

 

 

More important to me is the significant cold being modeled. My cold November stance is well noted and this cold snap is just what I was hoping for. Hopefully it comes to pass, even though I'm going on vacation to SW Florida next week and temps when I arrive there are forecast to be 15-20 degrees below normal. The normals where I'm going is 83/64 so probably looking at 70/50ish.

Man, we go to the Sanibel vicinity most summers.  Really like that area.   Definitely been eyeing the time frame next week.   Very strong, early season trough w energy rounding the base...lake effect machine gets cranking with most solutions.

[John1122]

3 minutes ago, Carvers Gap said:

Man, we go to the Sanibel vicinity most summers.  Really like that area.   Definitely been eyeing the time frame next week.   Very strong, early season trough w energy rounding the base...lake effect machine gets cranking with most solutions.

We're going to Marco Island. Leaving Wednesday evening next week. A week ago the forecast high was 86 upon our arrival. Now it's changed to 73/56.

[Carvers Gap]

Just now, John1122 said:

We're going to Marco Island. Leaving Wednesday evening next week. A week ago the forecast high was 86 upon our arrival. Now it's changed to 73/56.

I have never been to Marco but hear it is awesome.  Just a great, easy going area.  Yeah, the natives down there are going to be chilly with those temps.  It is a haul down there, but well worth it.  Hope you have a great trip.  

[AMZ8990]

27 minutes ago, John1122 said:

We're going to Marco Island. Leaving Wednesday evening next week. A week ago the forecast high was 86 upon our arrival. Now it's changed to 73/56.

Have fun on your trip, John.  Just don’t go bringing back any warm Florida air with you. :).  Next week does look interesting for sure,  I can’t remember how many years back it was but I do remember us having a November dusting on my side of the state several years back, maybe 2012 or 13.  Either way though it’s just fun to have something to keep an eye on!

[BlunderStorm]

The latest Euro and GFS have peaked my curiosity. In the eastern Tennessee Valley I have my eye on the possibility of the storm  around Tuesday taking a Miller A track.  If this were to occur and we could somehow get the cold air in place we might have a shot. Also, hope you have a good vacation John! 

[John1122]

The GFS went full on coastal craziness on us for Nashville and points east. We'd be fighting some ground temps for sure. and the height is in the afternoon, but the sun angle this time of year is similar to early February.  The Euro is well NW during this time with a major storm from Oklahoma to Michigan with some snow showers here chasing the back end. There was a member of the EPS that showed a similar event last night.

[Reb]

3 hours ago, John1122 said:

The GFS went full on coastal craziness on us for Nashville and points east. We'd be fighting some ground temps for sure. and the height is in the afternoon, but the sun angle this time of year is similar to early February.  The Euro is well NW during this time with a major storm from Oklahoma to Michigan with some snow showers here chasing the back end. There was a member of the EPS that showed a similar event last night.

This mornings GFS has doubled down on this idea and then some!

 

[Holston_River_Rambler]

I was really happy with how the EURO had been looking until this 0z, since there was something there, but it was suppressed with 7+ days for changes and trends. This morning's 0z EURO inland runner up the Apps is no bueno for me, but is only one run 6-7 days out.  Changes for better or worse are guaranteed. 

6z GFS, FV3 soon-to-be new GFS, 0z CMC are a little further south and less amplified. 

I only have access to the UKMET out to 6 days, but at MSLP it looks like a compromise between the oz EURO and 6z GFS. Same at 500 mb geopotential heights.

Looking though EPS members there seem to be 2 camps. One camp follows the Operational, one way or another: shallower or deeper, positive or more neutral tilted 500 trough cruising on through.  I think there is probably more to be said about the different possibilities within this camp, camps within camps, but I'm just not good enough at reading stuff that subtle and for me anyway, it's still too far out for me to want to.  The other camp is cutting off the main trough somewhere over the southwest or mid continent.  EPS average for MSLP on tropical tidbits is more SE. The crux for the Euro seems to me to be the energy that drops into the US this weekend: when, approach, and how that part works out. 

GEFS members. Quite a few have the dreaded Great Lakes low and 3 out of 17 have an inland runner as far west as the TN valley.  Overall though the members are still as SE or quicker with the whole progression than the operational.  

Overall thoughts: I'm glad there's some confusion on the models. I'm happy the Euro is at least seeing a consolidated storm in the Gulf. Also happy that a compromise between all these would be a good track for parts of the valley.  Although, I think I sound a little down in my ramblings on this potential storm, I'm not. Can I say something "feels" interesting about the whole set up without that being a kiss o' doom and without it being too banterish?

As I've said before this fall: We are talking about a real potential set up and cold in mid November.  There have been Januaries and Februaries lately where what we have coming up is the best we could do all winter.  Also, there doesn't seem to be a feel of a Miller B to this mess next week, whatever happens. Just a straight up Gulf low coming north. For my location anyway, I'd like a longer term winter pattern that features more Miller As than Bs and however this works out, if it is a taste of what's to come later, I'll be happy. 

[nrgjeff]

Great analysis by Holston River Rambler above; I have little to add to the already thorough objective analysis. Instead I will share my subjective thoughts.

ECMWF is wobbling so the EPS probably has more reasonable members than the Op. GFS-Para (FV3?) is not as robust as the GFS-Op either 00/06Z. Perhaps the Para is the proper middle ground among everything including the Euro. It does not give the Plateau much but the Smokies are of course in the game. Mid-November just the Smokies is still a good look for our region.

I've been posting about middle forecasts a bit recently. Saw a conference presentation that was quite interesting regarding combos. We all know ensembles beat ops. Even if a member is pretty bad, its combo with a good member still beats the good member alone. It does not match simple math or intuition. One must consider errors canceling out. So combining a model with 2% error and one with 4% error rarely gives 3% error. More likely, the combo error is below 2%! So, I go with the GFS-Para / FV3 this outlook.

[Carvers Gap]

25 minutes ago, nrgjeff said:

Great analysis by Holston River Rambler above; I have little to add to the already thorough objective analysis. Instead I will share my subjective thoughts.

ECMWF is wobbling so the EPS probably has more reasonable members than the Op. GFS-Para (FV3?) is not as robust as the GFS-Op either 00/06Z. Perhaps the Para is the proper middle ground among everything including the Euro. It does not give the Plateau much but the Smokies are of course in the game. Mid-November just the Smokies is still a good look for our region.

I've been posting about middle forecasts a bit recently. Saw a conference presentation that was quite interesting regarding combos. We all know ensembles beat ops. Even if a member is pretty bad, its combo with a good member still beats the good member alone. It does not match simple math or intuition. One must consider errors canceling out. So combining a model with 2% error and one with 4% error rarely gives 3% error. More likely, the combo error is below 2%! So, I go with the GFS-Para / FV3 this outlook.

Awesome.  I had to read that like five times before it made sense.  LOL.  

[Carvers Gap]

Through the first six days of November, TRI sits at +3.2.  We have hit 70 twice.  So, we will likely have a positive departure from normal during the first week of the month.  Now, the next 10-14 days should be cold.  Can we hold the likely negative departures that will result from the deep eastern trough?  I do think we see some warm air work into the pattern as things go zonal for an undetermined amount of time...the MJO likely supports that(some debate on how much amplitude the MJO will have as it passes through warmer phases).  I think it was the 0z EPS control where one can see the chinook winds warm the eastern foothills of the Rockies later in its run(edit: after this next cold shot).  That warmth will likely build and then head East.  Again, and I sound like a broken record, what happens immediately after that is of great interest.  What happens during November...the winter will remember.  That is why this cold shot might be a harbinger of things to come.  Like @John1122, I definitely want to see November finish on the cool side.  So it is weeks 1(and maybe 4) vs weeks 2 and 3.  

Now, notice I did not write about the Weeklies from Monday night.  I am wanting to see if that run was just a blip.  It was fairly warm in spots, but the run seemed a bit "buggy."  Whether warm or not, the run does not portend to a bad winter.  It only goes to about Christmas right now.  Also, the Euro Weeklies have not been exactly stellar(not unusual during fall for it)...though they did reasonably well for this current week.  And it is good to remember that the Weeklies are not really good at picking out singular events, but just with the overall pattern.  They are fairly accurate to week 3...so-so to week four...and decent if they see a flip between weeks 5-7 but not good with details then for obvious reasons.  I think they absolutely jumped the gun w the zonal pattern and missed the amplification of next week's trough...but will likely be correct w the pattern but not the timing.  I will gladly be wrong!  As noted, I am not a fan of warm fall weather.  

As for the snow, we have been kicking it around during banter...not trying to be snobs, that is just where we started talking about.  It is definitely worth discussion in this thread.   So, you can see some of my comments there.

Finally, great to see @Reb posting!  I know when @Stovepipe and reb start posting, winter is just around the corner.

 

[Carvers Gap]

It is a ways out there(many runs until the actual event), but thought I would share the vorticity maps. The 6z GFS dug a bit more and was slower.  The 12z GFS was a bit faster, and dug less.  I would not be surprised for models to overestimate how much something digs at this time of year.  Optimum is for something to dig to the southwest of the forum area, go neutral tilt as it passes, and go negative to our SE.  Plenty of things working against a trough and accompanying energy at this time of year.  Still, we have cold.  We have energy moving through a deep through.  Several solutions have it taking the low road.  Going to be a ton of different looks with that set-up and being this far out.  But hey, we have something to discuss on November 7th.  Even if just the mountains, I can live with that given how early in the season it is.

[Carvers Gap]

As for the longer range...and I have stated that after this deep trough there is potential for a time of zonal...but have also stated that what comes after that is what I am very interested in.  Here is a comment from PSU on the MA forum.  I mentioned the other day that somewhere I had read that zonal winds during El Nino(for better or worse it might have even been JB) can precede blocking up top and/or an early displacement of the PV.  Though not a scientific link, I thought the following comment was very interesting.  @psuhoffman, no need to respond, but letting you know that I mentioned your comment.  Hopefully, I did not butcher the intent.

 

[John1122]

The Canadian seems to be somewhere in the middle of the GFS and Euro. The Euro was even more of a Lakes event at 12 than at 0z. If nothing else the models are always consistently at odds with the exact evolution of events but seem to be better at sniffing out systems in the 7-10 day range than ever. 

[Carvers Gap]

57 minutes ago, John1122 said:

The Canadian seems to be somewhere in the middle of the GFS and Euro. The Euro was even more of a Lakes event at 12 than at 0z. If nothing else the models are always consistently at odds with the exact evolution of events but seem to be better at sniffing out systems in the 7-10 day range than ever. 

Agree.  Bout the best they can tell us right now is that we have a trough, energy rounding its base, and it will be east of the MS.  Typhoon had some good comments in the MA forum about how difficult it is for troughs to dig at this time of the year.  Models are likely struggling more so than normal given that it is November.  Definitely a window for amplification in the East.  I have no idea where within that area.

Edit...dug up the post from that thread.  Here is the link:

 

 

[John1122]

If we can pull this look off in winter I'll be pretty happy with it. I actually think it would probably be more snow than rain if it can come to pass next week.

[John1122]

0z GFS holds serve with it's far south/off shore solution. More widespread cold and snow showers for most of the state on that run with the system further south/east. Elevated areas see a few inches along the Plateau and Mountains. A dusting over most of the state, through I'd suspect more of a deck and rooftop type event.

Canadian moved closer to the Euro with an Apps runner. Still a decent ways to go but I wouldn't be surprised to see a cutter/Apps runner come to pass. Seems more likely than the GFS solution just based on climo this time of year and the general tendency of systems to be far more likely to cut west of the Apps vs east of them. Even with the Canadian solution most of the state would see backside snow showers, but that's often overdone on models and drying tends to happen much faster than modeled.

[Carvers Gap]

Week 1 observation: TRI will finish at +3.3.  TYS has is at +1.1.  Chatt is 0.0 for exactly normal.   Interesting range of temp departures.  

Near(er) term:  Nothing to add to John's comments.  Seems to have it covered. 

LR:  Just glancing at the 500 maps for the 0z EPS and 0z GEFS.  The EPS is moving forward in time the zonal flow now, roughly ten days out vs 12-15 where it has been.  The GEFS is also but to a lesser extent.  The temperatures react differently.  The EPS is warmer and GEFS is cooler.  Most of that is in my earlier posts...and that is not what interests me.  What is interesting?  The GEFS for a the past few runs is beginning to show some blocking in the right places, Alaska and Greenland.  It is likely ahead of itself, but that is a good sign and might fit with the progression that PSU was speaking about in the MA forum.  The EPS is trying to get there but has lower heights over both places(compared to the GEFS), especially AK.  But the looks are not overly dissimilar.   What does all of that mean?  For those with cold December forecasts, that is a step in the right direction.  I will be interested to see if the Weeklies hold serve with their warmer solution from Monday.  And even if December is warm, I still think winter will be fine.  There are some quick starting Ninos, but there is a cluster(maybe more...maybe significantly more?) that are colder from mid-winter onward.  That is the camp I am in...but I certainly will be hoping that the GEFS(even if it is too fast) scores with this.  Also, it will be interesting to see which model better handles the transition into winter.   (A quick glance at the FV3-GFS and it seems a debatably closer to the EPS...however, that is comparing the Euro ensemble to and operational model). I suspect that many of these differences(referring to the 500 pattern) are in how the various models are handling the MJO(per JB).

[John1122]

The 12z GFS is a Miller A dream track from the Plateau and West, if it were a month from now it'd be a state wide dream come true. That path from Lake City Florida to just ESE of Columbia, SC would bring home the bacon.  There have been unusual snows well South of us in recent years, it'd be nice if we managed one at one at some point in our region.

 

The Canadian went way south and looks to bullseye East Tennessee with it's latest run.

[nrgjeff]

GFS-Para / FV3 went with less snow. It is warmer, a bit of a cold chasing rain deal with the lead/main wave. Secondary wave gets snow at higher elevations. ECMWF is warmer, despite the surface low not cutting. Euro has northern vort max stronger, which as usual is bearish for snow.

At any rate I like moving the conversation from Banter into Fall Spec. It is a real forecast now. Euro is not always right, so at least I-40 north can hope.

[John1122]

1 hour ago, nrgjeff said:

GFS-Para / FV3 went with less snow. It is warmer, a bit of a cold chasing rain deal with the lead/main wave. Secondary wave gets snow at higher elevations. ECMWF is warmer, despite the surface low not cutting. Euro has northern vort max stronger, which as usual is bearish for snow.

At any rate I like moving the conversation from Banter into Fall Spec. It is a real forecast now. Euro is not always right, so at least I-40 north can hope.

The Euro has been as steady running the Apps as the GFS has been taking the low road. The Canadian seems to just bounce back and forth between the two.  At 500mb they are both very similar with the big western ridge. The ridge in the Atlantic is a little more westwardly prominent on the Euro and that shifts the storm track 200 miles west/nw on there. That ends up making all the difference in the world here between snow and rain.

[AMZ8990]

3 hours ago, John1122 said:

The 12z GFS is a Miller A dream track from the Plateau and West, if it were a month from now it'd be a state wide dream come true. That path from Lake City Florida to just ESE of Columbia, SC would bring home the bacon.  There have been unusual snows well South of us in recent years, it'd be nice if we managed one at one at some point in our region.

 

The Canadian went way south and looks to bullseye East Tennessee with it's latest run.

Nice to see these solutions continuing to show from run to run, definitely a real possibility that someone sees some wintry  precip:  I’ll be interested to see if the models have a similar solution Next run or if they lose the storm all together.

[Holston_River_Rambler]

Any thoughts y'all on the odd ball solution the 12z Euro has thrown out? An initial low runs up the apps (what we're taking about above), but that isn't the bulk of the energy now. Some 500 mb energy digs into TX, holds back a bit, and cuts off. It then rolls through the south in an ideal track for parts of our area. Maybe 1/3 of EPS members show some form of this, some better some worse regarding the energy's track. 

This energy is at least there on the 12z CMC, if much more positively tilted.

The 12z GFS has it too, but buries it in Northern Mexico and scoots it out, shredded across the gulf coast. FV3 shreds it out too. Maybe 3 GEFS members try something similar to the EURO/EPS with the energy. 

ICON is kinda trying at the end of its run. 

UKMET has it too, and looks quite a but like the EURO out to 6 days, but maybe 200 miles further west with the energy.  It looks like it is popping a low waaayyyyy down in the Gulf with nowhere to go but NNE...

Image is the UKMET at 12z next Wednesday (1 is MSLP and 2 is 500 geopotential heights). 

source: https://weather.us/model-charts/gbr/usa-east/sea-level-pressure/20181114-1200z.html 

source: https://weather.us/model-charts/gbr/usa-east/geopotential-height-500hpa/20181114-1200z.html