Fall Speculation 2018

[AMZ8990]

31 minutes ago, Carvers Gap said:

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....

  Wow, your right.  That is a pretty stout decrease for sure.  Late November/ Early December would be interesting if that comes to pass.  

[John1122]

Our western forum area folks are still in the game for winter weather later in the week, though sadly today/tonight didn't work out for them.  I hope they can pull off a few inches from the late week system.  The GEM and Euro are just about 50 miles outside of our forum area with decent accumulation. They should see flakes in the air if nothing else though. Possibly some icy mix in areas as well. There's also been a few hints at a clipper rolling through late next weekend but it might be a rainy clipper here with snow closer to the Ohio River.

The 12z GEFS keeps lower heights over the SE with almost no AN temps in sight as we close out November. 

The 20 coldest Decembers since 1948 (time of record there) in Crossville had 16 N/BN Novembers and 4 AN Novembers. 8 of the 16 were 2+ degrees below normal for November and 8 were within .5 degrees or less of normal for November. So I looked around the region to see how November led into December during that timeframe. Basically we want near normal or below if we want winter to start in December. 

At TRI 12 of the 20 coldest Decembers had N/BN Novembers.

At TYS 14 of the 20 coldest Decembers had N/BN Novembers. 

At BNA 14 of the 20 coldest Decembers had N/BN Novembers.

At CHA 12 of the 20 coldest Decembers had N/BN Novembers

At HSV 12 of the 20 coldest Decembers had N/BN Novembers.

At LOZ 13 of the 20 coldest Decembers had N/BN Novembers.

In Memphis it changed up, 11 of the 20 coldest Decembers actually had AN Novembers there.

So the weather we are seeing  across the area, N/BN,  is a better signal for a cold start to December across most of the valley vs an AN November where you hope for a flip to cold in December.  

As a note, it took 2 days for Tri to erase it's +3. It's now at +.2 for the month, or essentially normal.  According to how the next week plays out, it will be tough for it to finish AN for the month if the next weeks forecast comes to pass but it could if the flip to warm is dramatic.

The Canadian ESN are even colder than the GEFS and has the whole country in the freezer by the end of November.

With all that said, I wouldn't be shocked if the Euro was right and both the GEFS were wrong.

 

[Carvers Gap]

11 minutes ago, John1122 said:

Our western forum area folks are still in the game for winter weather later in the week, though sadly today/tonight didn't work out for them.  I hope they can pull off a few inches from the late week system.  The GEM and Euro are just about 50 miles outside of our forum area with decent accumulation. They should see flakes in the air if nothing else though. Possibly some icy mix in areas as well. There's also been a few hints at a clipper rolling through late next weekend but it might be a rainy clipper here with snow closer to the Ohio River.

The 12z GEFS keeps lower heights over the SE with almost no AN temps in sight as we close out November. 

The 20 coldest Decembers since 1948 (time of record there) in Crossville had 16 N/BN Novembers and 4 AN Novembers. 8 of the 16 were 2+ degrees below normal for November and 8 were within .5 degrees or less of normal for November. So I looked around the region to see how November led into December during that timeframe. Basically we want near normal or below if we want winter to start in December. 

At TRI 12 of the 20 coldest Decembers had N/BN Novembers.

At TYS 14 of the 20 coldest Decembers had N/BN Novembers. 

At BNA 14 of the 20 coldest Decembers had N/BN Novembers.

At CHA 12 of the 20 coldest Decembers had N/BN Novembers

At HSV 12 of the 20 coldest Decembers had N/BN Novembers.

At LOZ 13 of the 20 coldest Decembers had N/BN Novembers.

In Memphis it changed up, 11 of the 20 coldest Decembers actually had AN Novembers there.

So the weather we are seeing  across the area, N/BN,  is a better signal for a cold start to December across most of the valley vs an AN November where you hope for a flip to cold in December.  

As a note, it took 2 days for Tri to erase it's +3. It's now at +.2 for the month, or essentially normal.  According to how the next week plays out, it will be tough for it to finish AN for the month if the next weeks forecast comes to pass but it could if the flip to warm is dramatic.

The Canadian ESN are even colder than the GEFS and has the whole country in the freezer by the end of November.

With all that said, I wouldn't be shocked if the Euro was right and both the GEFS were wrong.

 

I think you will get near normal or below normal for all of the forum area.

I actually don't think the GEFS and GEPS are wrong...maybe just a bit too quick.  The EPS is likely dragging its heels again w the overall northern hemispheric circulation pattern, especially over North America at the mid-latitude.  It has been less than stellar this mont.  So, maybe something down the middle is a good idea?  Either way, it seems that all three ensembles(have not seen the 12z EPS) are evolving in similar fashion.  I think what we are looking at right now are just timing issues.  There is a bit of a model war going on w timing, but I like where all three models are heading.  

I wonder if cold Memphis winters correlate to moderate La Nina?  That might explain the warm November deal there.  I wonder how many weak La Ninas account for warm Novembers and then cold winters?  

My overall thought for December is that it would be slightly AN....this back-and-forth business is going to make it tough to nail a month down.  I am certainly hoping to be wrong!  I think the ensembles hint that December might get a head start with cold.  Still, thinks in the medium to long range have been lest than trustworthy.  So the goo and bad news is that everything is still on the table.  Even though isotherm's January and December are opposite of mine in terms of temps, I like that forecast and reasoning behind it.  Seems like many folks are going w February for the knock out.

As for TRI, I think today will likely send it BN and then it is just a matter of how low can it go and how much warmth that follows.

[Carvers Gap]

Here is where I think things are probably uncertain...in the MJO regions of the western Pacific and maybe even eastern Indian Ocean.  You can see that the American model is signaling a drop into the COD and across into phases that favor cold during December.(edit)  OTH, the Euro stays in the COD.  That might account for some LR modeling differences.  Either way, both are staying away from the real torch amplitudes and phases.  Just judging by the abrupt transitions...the models are probably playing a bit of catch up.  Seems like I remember that one of the models wanted to skip the warm phases altogether.  Can't remember which one it was.  So, it looks like a blend.  

The SOI is generally positive during Nina events and negative during Nino events.  So, we can see some conflicting signals in both indices and that likely accounts for the models struggling.  As isotherm mentioned, the increasing dominance of the El Nino event is probably causing some issues.

Quick study on the SOI from the LongPaddock:

The Southern Oscillation Index (SOI) is often used as an input for seasonal climate forecasting in Australia and other El Niño Southern Oscillation (ENSO)-sensitive areas around the world. We provide daily SOI data from 1991 and monthly SOI data from 1876 up to present day. We’ve also used the SOI to develop seasonal climate outlooks including rainfall probabilities and pasture growth outlooks for graziers and other land managers to freely access from this web site. These SOI datasets are generated automatically from third-party sources of Mean Sea Level Pressure (MSLP) that we access and so, occasionally there can be unscheduled interruptions to our service that are outside our control.

[Holston_River_Rambler]

Not to keep dragging this upper low Thursday back up, but NAM and EPS are trending deeper and more of a W - E progression than and SW - NE progression. EPS average is a track from Memphis to Cumberland Gap. Maybe someone even outside of extreme W TN will get to see a rare rain to snow transition even if it doesn't accumulate. Upper plateau and S KY and even TRI could be in for a few flakes. Wrap around moisture that actually wraps around for once? 

[John1122]

6 minutes ago, Holston_River_Rambler said:

Not to keep dragging this upper low Thursday back up, but NAM and EPS are trending deeper and more of a W - E progression than and SW - NE progression. EPS average is a track from Memphis to Cumberland Gap. Maybe someone even outside of extreme W TN will get to see a rare rain to snow transition even if it doesn't accumulate. Upper plateau and S KY and even TRI could be in for a few flakes. Wrap around moisture that actually wraps around for once? 

I'll be in Florida by then, so flakes are almost a guarantee. The Euro is very bullish for West Tennessee, even down to Memphis. Nice SE shift for those guys.

[AMZ8990]

59 minutes ago, John1122 said:

I'll be in Florida by then, so flakes are almost a guarantee. The Euro is very bullish for West Tennessee, even down to Memphis. Nice SE shift for those guys.

I’ve been keeping an eye on this the past few days.  It’s pretty cool how this system just popped up within the last few days.  It will be interesting to see what the high pressure over the Great Lakes does as the low down south pushes east northeast.  Ive got my fingers crossed that we can score some flakes!

[BlunderStorm]

After seeing tonight's run of the euro I am concerned about the possibility of an ice storm in SWVA Wednesday night into Thursday morning. I'm too tired to really delve into it tonight but this may be worth discussion for tomorrow.

[John1122]

The Euro was colder initially than prior runs, moderate ice storm across most of Kentucky, still moderate snow in West Tn with snow spreading statewide but in much lesser amounts as the system moves away.  NAM is very icy too, just crushes North Carolina, parts of NW Tennessee and the Western 2/3rds of Kentucky.

[Holston_River_Rambler]

For snow for folks Nashville west or upper plateau/ KY, it's all going to depend on where that upper low tracks.  At 72 hours (6 PM Thursday), the 0z EURO and CMC are further south (by maybe 50 - 100 miles) than the 6z GFS and NAM.  I counted 30 EPS members that were south of the 0z EURO operational. Around 10 0z GEFS members are south of that operational. American models trending slightly north the past 12 hours, EURO and CMC slightly south, and east.  But........the problem with looking for trends in this case is that it all depends on the time you use.  If I went back 24 hours from the above time, (to 6PM Wednesday) the EURO is actually trending north and east.

Bottom line for me is now wait and see. Upper lows gonna wobble.  I will say the trend for the weather W TN this AM has been colder and snowier than was forecast 24 hours ago. Even today's 6z NAM was showing rain for areas that are seeing snow right now, so hopefully some of you will see a similar trend as we get closer to Thursday.  Good luck to all out that way!  

Bad luck to all ice! As far as I can tell most models show the ice line setting up in the usual CAD place we talked about last winter (around a line from Tazewell south to Marion and then east), east of Blunderstorm. I hope all in the forum area are spared ice. 

[AMZ8990]

13 minutes ago, Holston_River_Rambler said:

For snow for folks Nashville west or upper plateau/ KY, it's all going to depend on where that upper low tracks.  At 72 hours (6 PM Thursday), the 0z EURO and CMC are further south (by maybe 50 - 100 miles) than the 6z GFS and NAM.  I counted 30 EPS members that were south of the 0z EURO operational. Around 10 0z GEFS members are south of that operational. American models trending slightly north the past 12 hours, EURO and CMC slightly south, and east.  But........the problem with looking for trends in this case is that it all depends on the time you use.  If I went back 24 hours from the above time, (to 6PM Wednesday) the EURO is actually trending north and east.

Bottom line for me is now wait and see. Upper lows gonna wobble.  I will say the trend for the weather W TN this AM has been colder and snowier than was forecast 24 hours ago. Even today's 6z NAM was showing rain for areas that are seeing snow right now, so hopefully some of you will see a similar trend as we get closer to Thursday.  Good luck to all out that way!  

Bad luck to all ice! As far as I can tell most models show the ice line setting up in the usual CAD place we talked about last winter (around a line from Tazewell south to Marion and then east), east of Blunderstorm. I hope all in the forum area are spared ice. 

I’ll take colder and snowier all day long,  if it comes to pass then I’ll have to give The euro some major Props since it was the first model to really start showing the cold/snow on my side of the state.  I’m Definitely intrigued and am keeping an eye on it.  We’re only 48 hours or less from this event so today’s runs will hopefully give us a better depiction of what will happen.   High is only 37 today too so it’s gonna be a chilly day!

[Carvers Gap]

7 hours ago, BlunderStorm said:

After seeing tonight's run of the euro I am concerned about the possibility of an ice storm in SWVA Wednesday night into Thursday morning. I'm too tired to really delve into it tonight but this may be worth discussion for tomorrow.

I would say the usual spots are at risk...places like Marion and eastward.  I think elevation "might" actually (famous last words) help you.  Also, I am not sure that I can ever remember an ice storm in this area during November....but never say never.  Give it a look at 12z, if you all are at risk...we can definitely make that part of the conversation.  I noticed the far northwest corner of NC was at risk as well.  We'll need to pay particular attention to where the high(to the north) is.  If it trends west of the Apps...sometimes cold can run into SW VA.  If it is east of the Apps, we get downslope and it stays warm enough.  I could easily be wrong...but wanted to make sure to discuss your area a bit.  All of SW VA gets ignored far too often in many aspects whether it be sports, politics, weather, etc.  

[BlunderStorm]

3 hours ago, AMZ8990 said:

I’ll take colder and snowier all day long,  if it comes to pass then I’ll have to give The euro some major Props since it was the first model to really start showing the cold/snow on my side of the state.  I’m Definitely intrigued and am keeping an eye on it.  We’re only 48 hours or less from this event so today’s runs will hopefully give us a better depiction of what will happen.   High is only 37 today too so it’s gonna be a chilly day!

It's always good news to have the euro on your side for an event. A few days ago when the models were teasing the possibility of snow over here the euro never really supported it at least as I recall. I hope yall get something out of this. 

7 minutes ago, Carvers Gap said:

I would say the usual spots are at risk...places like Marion and eastward.  I think elevation "might" actually (famous last words) help you.  Also, I am not sure that I can ever remember an ice storm in this area during November....but never say never.  Give it a look at 12z, if you all are at risk...we can definitely make that part of the conversation.  I noticed the far northwest corner of NC was at risk as well.  We'll need to pay particular attention to where the high(to the north) is.  If it trends west of the Apps...sometimes cold can run into SW VA.  If it is east of the Apps, we get downslope and it stays warm enough.  I could easily be wrong...but wanted to make sure to discuss your area a bit.  All of SW VA gets ignored far too often in many aspects whether it be sports, politics, weather, etc.  

I love snow and I can enjoy the novelty of sleet but freezing rain is where I draw the line and am typically not in favor of it. It's wet, yet at the same time freezing ,and all surfaces turn into an ice skating rink. Weather wise it would be interesting though. I have my eye on the back end of the event where cold air wraps around and I have a chance for snow the next evening/night. If the upper layers could just get a little colder maybe it could be sleet or perhaps snow early Thursday morning but I highly doubt it. I did notice the higher pressure north of here on the euro but the center of high pressure is still over New England.

[AMZ8990]

1 hour ago, BlunderStorm said:

It's always good news to have the euro on your side for an event. A few days ago when the models were teasing the possibility of snow over here the euro never really supported it at least as I recall. I hope yall get something out of this. 

I love snow and I can enjoy the novelty of sleet but freezing rain is where I draw the line and am typically not in favor of it. It's wet, yet at the same time freezing ,and all surfaces turn into an ice skating rink. Weather wise it would be interesting though. I have my eye on the back end of the event where cold air wraps around and I have a chance for snow the next evening/night. If the upper layers could just get a little colder maybe it could be sleet or perhaps snow early Thursday morning but I highly doubt it. I did notice the higher pressure north of here on the euro but the center of high pressure is still over New England.

Thanks bud, I was definitely glad to see the euro on board for this possible Wednesday/Thursday event.  It’s tough not to be cautiously optimistic with it on board.  It’s amazing How powerful this early season cold blast is!  I’m sure I speak for all of us when I say it’s wonderful to have so many weather events/variables to dive into and break down, especially in mid November!!

[John1122]

Right where the rain/snow line sets up will probably see the heaviest snow, tough to ever tell with these systems though, wobbles of 30 or 40 miles have major effects on the ground. I'd like my chances best in SW Kentucky or NW Tn still, not sure that the totals the models are throwing out will verify but I'd say they might in isolated areas. It's usually not a bad idea to shave off 40 percent of what they show.

[AMZ8990]

38 minutes ago, John1122 said:

Right where the rain/snow line sets up will probably see the heaviest snow, tough to ever tell with these systems though, wobbles of 30 or 40 miles have major effects on the ground. I'd like my chances best in SW Kentucky or NW Tn still, not sure that the totals the models are throwing out will verify but I'd say they might in isolated areas. It's usually not a bad idea to shave off 40 percent of what they show.

Great point John!  I’m just curious, what about the rain snow line makes you think that would be where the heaviest accumulation is? 

[John1122]

1 hour ago, AMZ8990 said:

Great point John!  I’m just curious, what about the rain snow line makes you think that would be where the heaviest accumulation is? 

Many times it's where the maximum amount of moisture that can still fall as frozen will set up. Basically the colder the atmosphere the less moisture it holds. It seems to play out often when it's snowing south of here along the northern gulf states. You'll see an area around 20-40 miles north of the rain/snow line that gets hit harder than surrounding areas.

[AMZ8990]

9 minutes ago, John1122 said:

Many times it's where the maximum amount of moisture that can still fall as frozen will set up. Basically the colder the atmosphere the less moisture it holds. It seems to play out often when it's snowing south of here along the northern gulf states. You'll see an area around 20-40 miles north of the rain/snow line that gets hit harder than surrounding areas.

Ok Cool, that makes perfect sense.  Thanks for explaining!  Hardeman County is now under a Winter Weather Advisory from 3AM wendesday to 6:00AM Thursday.  First one of the new season!

[jaxjagman]

As talked about in the severe thread two systems should effect us upcoming.The first one into next weekend which i thought could be severe but this afternoons Euro run shows the LP going through the Valley which wouldn't be severe,right now.The 2nd system tho could be the one to really keep an eye on.Chattownsnow showed the teleconnections in the winter thread and how he mentioned we was only missing the +PNA which was true at the time he posted this, this even seems to look even better today,towards the end of the month,you can now see a +PNA.East Asia shows a trough going trough around the 21st -22nd.notice the spike on the PNA today around the 28th ?Control and FV3 shows winter in the long range models.Definite some very good signals tho right now.

[Holston_River_Rambler]

Been trying to figure out what I think of the upcoming pattern/ PNA, AO, NAO. Lots of interest on other regions' discussions in the Dec. 1 or thereabouts time frame and perhaps rightly so. Ensemble means look nice and FV3 has been looking amazing at that time. Just can't quite get fully onboard just yet. Not because I don't think there is change coming or that it will not be great, but because I'm not sure how it plays out.  

Look how much uncertainty develops as the -NAO develops from the Scandinavian ridge: 

We go from not horrible disagreement at 500 mb in 140 hours or so, to a real spaghetti mess by hour 186. Apparently this is really messing with the model, although some of this may be normal Plinko/ ensemble progression. But for me this animation really shows how that block starts to choke up traffic and back it up, back it up, back it up. Like a traffic jam, upstream traffic buckles and becomes more convoluted too. 

I really want to get excited about the teleconnections, but I don't think models start to sharpen focus on what those could produce until the Scandinavian ridge migration is complete and it sets up shop.

By the way, this is not meant as a direct response to Jax above. I was just cruising around COD site this AM since Tropical Tidbits is down for server maintenance and noticed the spaghetti plots, something I don't normally look at. 

[jaxjagman]

Yeah even with the good teleconnections just not alot of cold air right now to work with what is  being shown

[tnweathernut]

This upcoming blast of cold air for Thanksgiving in the northeast wasn’t even on modeling just a few short days ago.  Gives me hope as we head into December....

[jaxjagman]

2 hours ago, tnweathernut said:

This upcoming blast of cold air for Thanksgiving in the northeast wasn’t even on modeling just a few short days ago.  Gives me hope as we head into December....

GEFS was slightly cooler tonight,even  shows some snow starting around the 28th tonight in the Valley.Still in the long range tho.

[Carvers Gap]

I grabbed this from JB's video yesterday.  It is the departure map for November.  I think it likely does a good job of showing us why the average temps are "warmer"(relative term as we are around -2) at TRI.   TRI is on the outside envelope of the bigger cold that has rushed down the Plains.  One other note, the SOI has begun dropping which is significant for several reasons...Often that signals a stormy pattern upcoming, and it likely means the El Nino is taking over for good at this point.

[Holston_River_Rambler]

10 minutes ago, Carvers Gap said:

Often that signals a stormy pattern upcoming, and it likely means the El Nino is taking over for good at this point.

Even though I think there are still surprises left with the developing blocking and northern stream evolution, one thing keeps showing up, run after run: gulf or southern lows of some variety or another. 4 on this morning's GFS run.   Track, temps, precip. all still uncertain, but storms are coming in starting late next week through early Dec. 

[Carvers Gap]

IMHO, the 12z GFS is the pattern that you want...not really commenting on particulars.  Cold highs coming down the Plains w a suppressed storm track that likely will come north given the time year.  If it was January, I would be worried all of that would go to New Orleans.  But late November into early December, that likely trends back north. Overall, have to like that look. Not sure that verifies, but you would think that is how the pattern "might" look given the CPC teleconnection ensembles.  Still, I really wish we would see that pattern about two weeks later.

[nrgjeff]

Euro Ensembles seem to agree with that southern storm track in the 11-15 day. I'm jumping ahead of the 12Z package, but figure it won't change much. Looks like 1-2 try to cut but 1-2 slide south. Cold air and vort max tracks will remain a mystery until about 5 days out.

I'm also interested in the weeklies tonight. Will comment on Tuesday unless I become unexpectedly free this evening, or the weeklies are particularly incredible. My Euro weeklies comments will likely go in December spec.

[Holston_River_Rambler]

So here's a question, but first an explanation of why I'm asking. Anthony Masiello tweeted an image of the N. Pole yesterday and was writing about the tropospheric vortices forming a "doughnut" around a high at the N. pole. Here's my version of this from the GEFS this AM: https://imgur.com/a/LMxZmqH.  This is on the EPS too.  

Now, Masiello was making a point about the Greenland block and possible repercussions of the evolution of all this in terms of NE snow, but my question is about that high at the north pole. Is this a way to build up some very cold air there? Having a big high just set up there with limited if any sunlight seems like it would create a nice airmass. Obviously no guarantees on where it dumps if it does develop and produce cold. But is that even how any of this works? 

 

[Carvers Gap]

39 minutes ago, Holston_River_Rambler said:

So here's a question, but first an explanation of why I'm asking. Anthony Masiello tweeted an image of the N. Pole yesterday and was writing about the tropospheric vortices forming a "doughnut" around a high at the N. pole. Here's my version of this from the GEFS this AM: https://imgur.com/a/LMxZmqH.  This is on the EPS too.  

Now, Masiello was making a point about the Greenland block and possible repercussions of the evolution of all this in terms of NE snow, but my question is about that high at the north pole. Is this a way to build up some very cold air there? Having a big high just set up there with limited if any sunlight seems like it would create a nice airmass. Obviously no guarantees on where it dumps if it does develop and produce cold. But is that even how any of this works? 

 

Normally, we do no want a tight vortex on the pole...we want it disturbed where it sends pieces southward.  Some may argue that it is better for it to be stable now and then perturbed later.  It "seems" like he might be saying that the polar vortex is likely going to have trouble tightening up...which means it will send cold air south pretty consistently.  I take it to mean that the vortices will send waves into the PV and dislodge pieces of it or force it towards one side of the pole.  Additionally, it may mean that those repetitive shots of air are not as cold as they could be, because the vortex never tightens up.  Would it be possible for you to post the tweet?  Sometimes he will post other tweets in relation to it that gives some context.  He has had some pretty interesting content this fall as usual.

[Carvers Gap]

 

I think this is the tweet.  Yeah, after reading the rest of his preceding and follow-up tweets...I am pretty sure I only understand about 10% of that.   LOL.  Maybe discussing the formation of the NAO, storm track, and pretty much that it just looks cool.  You can see the heights rise over the Davis Straits at the end of the loop.  IMHO, the million dollar question is whether it holds or whether the other vortices quickly wipe it out as they rotate around.  He has some incredibly detailed tweets about the NAO that were recently posted in relation to the Scandinavian Ridge...but again, some of that is just over my head.