Tennessee Valley 2019 Fall Speculation/Forecasting

[Snowy Hibbo]

G’day everyone.

I would just like to present my preliminary seasonal outlook for the Northern Hemisphere, which includes driver discussion and analysis for patterns that run downstream to the Tennessee Valley

https://longrangesnowcenter.net/2019/10/12/october-preliminary-2019-20-winter-outlook/

1. Snow & Ice conditions good for Eastern US, Japan and Europe/UK.
2. MJO largely good for European and UK snowfall, perhaps less so later in winter. Similar for Eastern US and Japan.
3. Oceanic ENSO good for Japan, Southwest US and Eastern US.
4. -AAM good for Europe, Eastern US and Japan, less strong later in winter.
5. Stratospheric conditions favourable for Eastern US, Japan and Europe/UK.
6. Solar minimum favourable for more snowfall for Eastern US, Japan and Europe/UK.
7. Atlantic favourable for a snowy UK winter and colder Europe.
8. QBO favourable for Eastern US, UK and Europe.
9. North Pacific favourable for Eastern US, less so for PNW.

“The Eastern US looks like it is set to have a good season as well, focused from the Central US early in the season, but more open to Nor’easters later in the season.“

Just to be more specific for the Tennessee Valley, I’d favour an average season in terms of cold, with lower temps favoured in the early-mid season, less so in the later season. I’d say a slightly-significantly above average snowfall season.

[Carvers Gap]

The 18z GFS...Well.  LOL.  And, I thought I was cold with it being in the mid-50s last night!  In all seriousness, I get a bit nervous when the GEFS and the EPS begin to get in lock step about potential cool downs - been some notorious misses recently.  Sometimes it is a "to good to be true scenario."  I am sort of in a "I have to see it to believe it" mode.  However, if one were to take the 12z GEFS/EPS suites, that is not a warm look.  That trend has been in place for a few days.  So, one would expect operational models to now start spitting out some pretty wild looks from time to time reflecting what the ensembles are doing.  I just want a day where we have highs in the 40s where I can tell my grandkids someday that...one time in October we set four straight record highs only to have highs in the 40s later that month.   It was definitely surreal last evening as I was sitting outside in very light drizzle, a light breeze, and temps in the 50s in Johnson City.  People, I forgot to bring a stinking coat or even a shirt with long sleeves!!!!  All of these bands from all over the SE, which have been practicing in record heat, were almost certainly dealing with similar situations.  Great and memorable evening for sure.     

[jaxjagman]

MJO signal looks weak again.Just when you would think the IO would die off again it get's resurrected by easterlies killing the MJO signal.This also looks like this could be the strongest easterlies upcoming the next several days into the IO,maybe it will move forward the end of the month?See what happens,looks like a warm up into the end of the month into the first of Nov tho

[Carvers Gap]

As I dig a bit deeper(catching up after being out of pocket since Thursday PM)....modeling looks to have maintained a look where the SER only briefly bounces back next weekend and then it looks like maybe 1-2 pretty strong cold fronts move in later in the month into early October.  No idea if true at this range.  Modeling is yet again signaling a pretty significant pattern change.  Does it hold or is it muted or even real?  Time will tell.   While the last "step down" was certainly muted, high temps are roughly 10-20 degrees cooler(depending on what days being compared) than even ten days ago.  Temps are still AN, but tolerable to even pleasant.  Looks to me like some true fall temps are going to show up during the coming 2-3 weeks.  Easy prediction since it is fall...but given the past mega-ridge, I was beginning to wonder if fall would show.  Interestingly, SE KY has a special weather statement posted for scattered frost tonight!   It is important to note that some pretty warm air not unsurprisingly surges northward between cold fronts.   I would not be surprised(as I noted in earlier posts) to see yet another record high or two posted.  What I think might be interesting is that a record low might be approached as well due to the sharpness of the ridges being modeled on operational and ensembles.  (That EPS ridge/trough look was not warm. )  I think it likely a lock that October finishes AN.  Those first four days and the slow step down to tolerable temps thereafter(still well AN) pretty much assured that.  Looks like TRI will have some highs in the 60s this week with even some low 60s possible.  Within roughly 14 days of the mega ridge, that would mean that high temps have dropped by roughly 30 degrees.  Again, I think we see a bounce back but not weeks-on-end of that heat ridge.   While it was cold last evening while sitting outside, I think most(while cold) were thankful to see those mid90s temps gone.

[jaxjagman]

Hagibis is still going to be a player into next weekend along with seemingly a Kelvin Wave into the Gulf which is being shown right now,next weekend and maybe into the first of the week after  right now to me could be rather volatile 

[nrgjeff]

Dry soil may be helping the temperature swings. We are not yet to the time of year where snowpack north is needed for cold anomalies. Dry soil can allow cold fronts to settle in now that the SER is broken. At the same time the Gulf Coast and Florida remain warmer than normal. Return flow will pop temperatures between fronts.

Front parade continues. Looks like midweek and again early next week; warm in between. Another front is forecast in the less reliable 11-15 day period. Then weeklies try to warm up after November 5th. Should I wait for the Euro weeklies tonight? Well, none of the weeklies are reliable out week 4 and it's shoulder season, so it does not matter.

Bottom line: Need to see continued march of the fronts into mid-November. By the the first of Nov, models will have that forecast period. Jury is still out on a long-term pattern change, just shoulder season shuffle, or return to AN temps.

[Carvers Gap]

I would not be shocked if this is the pattern for winter....cold builds over the Rockies and then rushes East with pockets of very warm air pushing up the east side of approaching fronts in between.  Obviously, it will be less warm as the winter progress, just speaking of comparative norms.    The seasonal models and even Weeklies bounce around from western trough to mid-continent trough for DJF.  I think that might be because this winter could potentially feature a fairly progressive pattern where winter starts out West and builds eastward.  I also realize that October is not a great indicator of winter.  However, with the snowpack building over western Canada, at some point that cold air mass will move SE.  Also agree that it is difficult to tell if this is a shake-up due to wavelengths or is an actual pattern change...but it is certainly different than the mega ridge.  As a numbers game, I just think another big western winter is less likely, though I do think they get going strong in December....but the West has been due for big winters after the 90s which was a terrible decade in terms of water if I remember correctly.  However, we are long overdue for a pattern change and wx models are notorious for perpetuating old patterns.  No idea, but that is part of what makes weather a great hobby....And hey, the Vols even won!  Might be that their play teleconnects well to the SER.  Big SER beginning this weekend, and of course the Vols play at Alabama.  Might be something to that.  

[John1122]

I'm not sure if it makes much difference at all, but the snow cover in the NH is much more expansive right now than last year at this time in our source regions. Last year NE Canada had more snow than this year. Russia, Siberia, Alaska, Western Canada and the upper Midwest are far more snow covered at this time vs last year on this same day.

[raindancewx]

My take on the very cold NW/very hot SE this October is that the PDO is going negative. Look at where the biggest anomalies v. the correlations are (granted, they are for winter, but with the NAO negative its a pseudo winter pattern now). Blending Nino 1.2 in October (currently under 20.0C on the weeklies) with the PDO in Mar-Aug (+0.83) to match 2019, you have to pick something like 1988-89 and 1996-97. I've hindcasted this method, it's remarkably strong as a predictor once Nino 1.2 is known in October. 

Analog	PDO M-A	Oct 1.2	PDO N-A
1988	0.86	19.81	-0.60
1996	1.06	20.31	0.38
Blend	0.96	20.06	-0.11
2019E	0.83	20.00	???

This was the blend I used to estimate the PDO last year.

Year	Oct 1.2	PDO M-A	PDO N-A
1963	20.96	-0.75	-0.88
2002	21.39	-0.24	1.69
2004	21.16	0.57	0.47
2004	21.16	0.57	0.47
Mean	21.17	0.03	0.44
2018	21.13	0.07	0.51

[Carvers Gap]

1 hour ago, raindancewx said:

My take on the very cold NW/very hot SE this October is that the PDO is going negative. Look at where the biggest anomalies v. the correlations are (granted, they are for winter, but with the NAO negative its a pseudo winter pattern now). Blending Nino 1.2 in October (currently under 20.0C on the weeklies) with the PDO in Mar-Aug (+0.83) to match 2019, you have to pick something like 1988-89 and 1996-97. I've hindcasted this method, it's remarkably strong as a predictor once Nino 1.2 is known in October. 

Analog	PDO M-A	Oct 1.2	PDO N-A
1988	0.86	19.81	-0.60
1996	1.06	20.31	0.38
Blend	0.96	20.06	-0.11
2019E	0.83	20.00	???

This was the blend I used to estimate the PDO last year.

Year	Oct 1.2	PDO M-A	PDO N-A
1963	20.96	-0.75	-0.88
2002	21.39	-0.24	1.69
2004	21.16	0.57	0.47
2004	21.16	0.57	0.47
Mean	21.17	0.03	0.44
2018	21.13	0.07	0.51

Good info.  I am not following that first PDO map, though - labels don't seem to fit or my mind might be missing the point....Anyway, -NAOs though usually signal very warm temps here during summer and early fall.  No surprise there as that teleconnection has been accurate.  As you noted the -NAO signal then converts to a cold signal during winter.  Not sure when that -NAO finally begins to help us...but it has kept us abnormally warm for much of early fall.  The cold off western SA definitely will be in play and may have consequences that equal the north PAC.  It is a bit of a Nina signal, even though a Modoki is likely.  That ENSO area has a tendency to signal a pretty good SER in early winter and then the SER collapses mid-winter.  Will be interesting to see if any big storms or deteriorating typhoons impact that warm water in the GOA.  That warm water will have a tendency to push AN heights into AK.  That is where things get tricky.  The past couple of winters have had the cold tuck almost underneath an Alaskan ridge.  What is tricky is that if that kink in the jet (which is allowing for that cold under that high) resolves, the cold comes East.  I tend to think this winter will feature more of a progressive pattern with cold building in the NW and then heading SE, sometimes severe in nature.   Of note, I have seen several seasonal forecast predict a +NAO for this winter which would make since it has been negative for much of summer.  So, I do agree that the Pacific will have to deliver cold as the Atlantic may be tough to convince.  That said, seasonal weather models last winter were about as bad as I can remember.  I still tend to believe that winter sets up shop in the Rockies for December and then spreads eastward during January and February.  As PSU noted in the MA forum, tons of conflicting signals this winter and it is just tough to know which one.  I agree that the oceans will likely drive it, but which signal....the Indian Ocean, the MJO, a falling or stalled QBO, PDO, warm ENSO in the mid-PAC, cold signal in the eastern PAC, a warm GOM, etc?  Lastly, we are way overdue for a pattern change.  This has been pretty much locked-in for nearly ten months.  It can't stay there forever.  But I guess it is always safer to bet the streak.  

I will comment a bit more on the Weeklies tomorrow.  The do look colder for weeks 1-4ish.  That said...shoulder it is season and the bust potential is always high.  

[raindancewx]

The first map is a correlation map, so the yellow/green colors mean positive correlation, i.e. when the PDO is negative the NW is cold. The blues/purples mean negative correlation, so when the PDO is negative, the SE is warm. The opposite is also true, positive PDO means cold south (negative correlation), positive PDO means cold northwest (positive correlation).

The cold ring of waters by Alaska and then the warm tongue of waters east of Japan - that is the canonical -PDO image 

[John1122]

It's odd that the graphics suggest warmer than average temps here during the -PDO but during the -PDO of the mid 1940s to the late 1970s we saw our coldest and most snowy winters. In te core of that -PDO that started in 1947, from 1955-1970, for instance was far far cooler on average in winter than the 1985-2000 period in the + PDO that flipped in the late 1970s. ;Looking at the graphic below, you can almost match it up that when it's in the warm or +PDO phase, it's warmer than normal here, when it's in the cool or -PDO phase, it's cooler than normal here.

[Carvers Gap]

IDK...gonna have to dig a little bit.  I do understand the correlation map...the labeling of -PDO=warm for the SE is throwing me off.  We may have to disagree that is a textbook PDO.  To me that gradient is not sharp enough around the edges.  One thing that Typhoon Tip has stated is that the lack of gradient is creating issues with analog years in the Pacific, in some cases actually resulting in the opposite of what one would think should happen.  Jeff has alluded to that as well.  The above ideas have definite merit.  Will have to give them a closer look when I have time.  Below is a textbook -PDO with a very sharp gradient with waters found near coastal AK and Cali/Baja.  Right now, the Pacific does not have that sharp of a gradient in those areas.  It is close by definition, but very muted w a poor gradient IMHO.

Reference: https://climate.ncsu.edu/climate/patterns/pdo

[Carvers Gap]

Yeah, John beat me to it.  -PDO here is not a slam dunk warm winter by a long shot.  What is tricky(and my mind is tired...will have to pick this up tomorrow) is that knowing when the PDO and ENSO are both in phase or out of sync.  Right now, that pool of water of SA being cold is going to be a forecasting headache.  One could argue that the PDO and ENSO are actually of similar phase if one looks at the mid-PAC,  but one could also argue that the are out of phase given the colder anomalies off of SA.  Again, conflicting signals.  I will keep rolling with my thoughts in June...but I am not supremely confident in any look right now.  My mind says that +NAO is gonna be a problem.  My gut says that the seasonal models will be wrong again this winter.  Low of averages is going to eventually end the cold over the NW.  The SE is tricky business and the TN forum area is even trickier.  Again, I don't have a ton of confidence in any solution...but I do like less of a locked-in pattern this winter for any region.   That said, that is just borderline guessing right now.

[Carvers Gap]

Great discussion by all BTW.  Going to hit the sack.  0z suites are rolling.  Plenty to discuss tomorrow.  Will be super interesting to see if the QBO drops again this month.  Also, low solar can cause some crazy effects as well and produce opposite results of common analogs.  Anyway, my mind has gone to mush at this late hour.  Cheers!

[Holston_River_Rambler]

Wish I felt more confident writing about the long term so I could contribute more, but after all the time I spent trying to figure out last winter and repeatedly getting my tail handed to me I'm sheepish.  

I know the Atlantic has the AMO, but does it have any other sea temp indices? The Pac has the PDO and ENSO, but the Atlantic only gets that one? Maybe since it is upstream of the US, when meteorologists were studying these indices the Pac got more attention, or maybe the Pac is just bigger and more important for NH patterns. What doest he PDO do exactly? Is it impactful for the convection influencing the polar jet and how that interacts with MJO fueled Hadley cells further south? 

As far as Pac sea surface temps go in ENSO zones, I feel like last year taught whipped me to wait and see where the convection pops and behaves after the MJO becomes active and influential for NA. Is the Pac still really warm basin wide? As anomalously warm as last year? Not rhetorical questions, and I'm guessing it is, but I can't remember where the anomalies were and how they looked last fall/ winter. Looking at the current sea surface anomalies, if I just eyeballed that from an admittedly hobbyist POV, looks Ninaish for now, but with little warm water to fuel convection in the usual Nina MJO location. Sure enough, current satellite reflects that:

But according some discussion above (maybe back a bit), in our ENSO thread, and Lord Masiello of Wxtwitterlandia, some form of ye olden Modoki may be on the docket? And indeed there do seem to be some warm bubbles westward in those ENSO zones. But like I said above, I feel like I want to wait and see where the convection tries to set up since all the warmer areas and even the areas where there is a contrast between abv. and below normal SSAs can have a say as well. Here is something I found while trying to find a ENSO subsurface map that might be even more helpful for this convo than the map I was originally looking for:

 

 

At least there is some certainty hope  for drought relief, esp. for eastern forum areas:

 

[Carvers Gap]

I agree with Jeff that the Weeklies are notorious for being wrong during shoulder season, mainly outside of week four.  So, even though last night's run supports some of my thoughts...those thoughts are no more right nor wrong than they were yesterday prior to this run.  So, right now I am just sharing a 30day 500 map from d16-46.  The Euro Weeklies have slowly evolved to this vs just one big flip.  Are they right?  No idea.  Again, 2m temps past wk4 are just raging warm and likely incorrect.  It is going to be cold and significantly cold somewhere in NA.  I will say, I really wish we had that look in January.  Features that are present:

1.  Kind of a hybrid PNA/EPO ridge

2.  WAR(Western Atlantic Ridge)

3.  Blocking over Greenland and over most of the pole.

4.  Eastern trough centered a bit too to the east to really deliver news making cold to our forum area.  NE might be really cold.

5.  Likely a coastal/inland storm track as systems run into the WAR.

Long story short.  Looks very much like the pattern for the next weeks just being repeated.  Huge if...but if that verifies, the trough over eastern NA is likely stronger and the ridge out West stronger.  Fly in the ointment would be that the pattern retrogrades some late in the run.  The WAR gets into the NE.  But again...it is shoulder season and I can just about guarantee that map is going to change and likely for the worse as that is about as good a 500 map as one can get at that range - if you like fall that is.

3.  

[Carvers Gap]

As for winter...man, I was tired last night and hope my posts weren't too disconnected.  Shew.

Anyway, winter at this latitude and elevation has never been a slam dunk.  It is really going to depend on whether cold air and moisture get into the pattern at the same time.  Bad patterns can produce snow and good patterns can be snowless.   So really, at this range we can only guess the pattern.  Last winter looked like a slam dunk to many, and it never materialized.  For me, I thought December would be warm but Jan/Feb cold.  Hit the first and missed the second two.  All three were warm.  At this point, just need to see where the cold sets up shop...and where the storm track is.  I remember us all seeing those awesome runs of the Euro Weeklies...and then Jeff noting, "....but the storm track is over Kansas."  Indeed it was and indeed it stayed there.  So, going to have to see where the cold and storm track sets up.  Fun to speculate though!

[nrgjeff]

All the answers are in Kansas, lol! 

OK to get serious. lots of solid posts above this page. I'm staying warm winter unless I see some big cold in November. October simply does not correlate. Weeklies are trash weeks 3-4.

PDO is indeed trending down. It's positive right now, but West Coast waters are rapidly cooling on the dT charts. A -PDO is a strong SER signal all else equal. Coldest years here were accompanied by -AMO. Both negative, is cold and stormy coast-to-coast. A -PDO +AMO is really mild here. Both positive is mild coast-to-coast (too much warm water).  Finally +PDO and -AMO gets you those 1980s arctic outbreaks. The two are out of phase about a half wavelength. This winter looks great again in Kansas, not so much East Tenn.

Modoki look to El Nino is not enough if we go -PDO. A -NAO is not enough either without help post-climate-change. Shift everything north. -NAO blasts the GL to NE. We sit south of the jet stream, actually going mild. Used to only be a hot signal summer. Getting mild winter now. 

Pattern shapes up like 02/03 or solar cycle 07/08 and 08/09. All were cold nationally and burned a lot of gas. All were also meh Southeast US. Solar 09/10 is next winter. After softening my bearish stance over the weekend, I'm back in the solid mild winter camp.

To go colder I would need to see big cold outbreaks early November with the start of some strato warming in the 6-15 day models. While the 11-15 day is a joke at 2m it is somewhat reliable in the stratosphere.

[John1122]

The EPO has been predominantly negative since June, if we can keep that up, it could make winter interesting. It drove winter for several seasons in a row when all the other teleconnections looked bad. 

[Carvers Gap]

Very good points about the PDO.  I do think the SST gradient is making some usually dependable indices less dependable.  Also, agree that the -AMO did help to offset the POD during the 70s.  It is a good example of how a favorable Atlantic can really help.  

Also, good points by John about the EPO.

Going to be interesting last to which drivers really have the most influence.  Last winter, my ideas were actually warmer than most forecasts even with my backloaded winter idea, but not still not anywhere close to being warm enough.  

If the Weeklies from last night verified, I would feel really good about winter...but no way I am dying on that hill just yet(meaning one run of the Weeklies).  LOL.   

Seriously, the discussion on this page has been stellar.

[Carvers Gap]

Some fun stats.   TRI had 44 straight days of AN temps until yesterday when its departure was -2.  During that same time frame, MBY(airport had a little more precip due to a few more showers) had  just 0.1" rain.  Saturday's high of 71 was TRI's coolest high temp since May 15th just looking quickly at things.  Temps will likely be below normal to well below normal on Wednesday and Thursday and Friday with highs struggling to reach 60 on Thursday.  Looks like Friday AM has an outside chance of scattered frost with lows approaching the mid30s.  The high on Thursday will be nearly 30-35 degrees cooler than it was just two weeks ago.  It has been a remarkable transition.

[Carvers Gap]

On 10/5/2019 at 11:14 PM, Mr. Kevin said:

Hi nrgjeff, i am kevin from ne arkansas. Ive read your posts for years and i am finally commenting. I have a few questions. I know its only October, but do you think it should be a colder winter than last winter? From my understanding, and correct me if i am incorrect, but if the IOD remains positive and qbo drops, wouldn't that allow a trough more in the central/east with mjo staying or tendency to stay in phase 1-2 most of winter, which are colder phases? Perhaps you believe the coldest weather will be west of the southeast US? Thanks in advance.

Glad to have you posting on here.  I look forward to more posts.

[Carvers Gap]

FWIW, the d10-15 EPS is pretty cold....time will tell.  

[Carvers Gap]

Lastly...what a welcome sight!

[John1122]

4 hours ago, Carvers Gap said:

Some fun stats.   TRI had 44 straight days of AN temps until yesterday when its departure was -2.  During that same time frame, MBY(airport had a little more precip due to a few more showers) had  just 0.1" rain.  Saturday's high of 71 was TRI's coolest high temp since May 15th just looking quickly at things.  Temps will likely be below normal to well below normal on Wednesday and Thursday and Friday with highs struggling to reach 60 on Thursday.  Looks like Friday AM has an outside chance of scattered frost with lows approaching the mid30s.  The high on Thursday will be nearly 30-35 degrees cooler than it was just two weeks ago.  It has been a remarkable transition.

It's wild how much warmer you've been than my area when we normally have similar temperatures. 

[Mr. Kevin]

5 hours ago, Carvers Gap said:

FWIW, the d10-15 EPS is pretty cold....time will tell.  

Carver, i am not sure its a good thing to see it real cold this early. I live in Arkansas, but that may not make any difference. It was cold last November and in 2011 and the following winters blowtorched. Alot of interesting signs already. 

[John1122]

3 hours ago, Mr. Kevin said:

Carver, i am not sure its a good thing to see it real cold this early. I live in Arkansas, but that may not make any difference. It was cold last November and in 2011 and the following winters blowtorched. Alot of interesting signs already. 

 

I'm not 100 percent sure for NE Arkansas, because it was less a correlation for Memphis than the rest of the great valley, but looking into it last year BN Novembers produced memorable cold/snow/ice outbreaks in about 7 of 10 winters. Unfortunately last year didn't work out so well for most of us, falling into the 3 in 10 that don't work out so well. I know for my area a cold November is something I'd rather have on my side than not. Warm Novembers fell flat about 7 in 10 times during winter. With both those said, it seems like analogs are less useful these days in the new climate normals we are seeing these days.

[Windspeed]

Nice..

[PowellVolz]

Strong system first of next week. MRX already thinking 1-2” across the board.


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