Fall 2017 Great Tennessee Valley Outlook

[nrgjeff]

Apps runners all winter. Depressing.

[John1122]

Apps runners can work well, especially for the western half of the valley, so even if it didn't do that much here, I'd like it for the western folks to get some nice winter storms. Plus, some of the most absolutely beastly winter storms in the history of the area were apps runners. Someday another of those will happen. We used to receive huge 12-20 inch snows across a large part of the entire valley at least every 10-15 years.  Not sure when the last really widespread one was. Knoxville probably hasn't recorded a 10+ inch snowfall since 1993. 

 

Best case scenario tracks for winter storms in the Valley are these two. With the clipper systems that dig being a 3rd.

1)

 

2) 

[John1122]

I am much more encouraged too, by the QBO now that I've been looking more at what Carvers spoke of regarding it's effects on blocking. In it's easterly phase the -NAO is much more common that when it's in it's westerly phase, though it's no lock that it will bring the -NAO/AO.

It was supposed to flip back towards easterly last December but was delayed for the first time in decades of observation. Now it has flipped back easterly and will be in the easterly phase for the next year or so as it cycles.

There were excellent maps posted yesterday in the SE form regarding -NAO and it's effects in La Nina years. As I've often observed, the drivers of NAO/AO/PNA/PDO far outstrip the ENSO factor in our weather. The maps posted yesterday confirm that. -NAO/AO La Nina winters were frigid in the East. +NAO/AO winters were very warm.  

The QBO being neutral or negative didn't always mean a great winter. But many of our notable winters were negative or neutral QBO years. The same with the +QBO, not all were bad winters but most of our warm winters featured the QBO in it's deep westerly + phase. 

Sometimes you have winters where nothing seems to apply. Winter 2010-2011 was fairly cold and very snowy for me. The QBO was positive. LaNina was strong. The February NAO was was mildly positive. The PNA was negative and I still manged multiple February snow events in a strong La Nina year. The temps weren't subzero frigid in 2010-11 but they were cold enough to make for a good winter despite most indications that it shouldn't have been one, with snow events in December, including a large White Christmas, and several in January too.

[Carvers Gap]

Thanks to all of the posters who are making this a great thread.  Some really good stuff.

Recent model runs of the Euro and GFS and ensembles are pretty cold beginning next weekend.  Hoping to fire-up the wood stove.  We will see where the Euro goes this afternoon.  The 0z EPS was chilly.  Seems a recent trend is a above normal heights over Alaska days 10-15.

[jaxjagman]

On 10/20/2017 at 1:48 PM, John1122 said:

Apps runners can work well, especially for the western half of the valley, so even if it didn't do that much here, I'd like it for the western folks to get some nice winter storms. Plus, some of the most absolutely beastly winter storms in the history of the area were apps runners. Someday another of those will happen. We used to receive huge 12-20 inch snows across a large part of the entire valley at least every 10-15 years.  Not sure when the last really widespread one was. Knoxville probably hasn't recorded a 10+ inch snowfall since 1993. 

 

Best case scenario tracks for winter storms in the Valley are these two. With the clipper systems that dig being a 3rd.

1)

 

2) 

The western parts probably cringe over these maps.The Valley has so much diversity pertaining weather it's not even funny.Storm track is so crucial,someone unless it's a super storm is going to basically miss out.

[Carvers Gap]

The 12z GFS...I know it is the GFS...hard not to like it.  Repeated shots if cold into a trough that buckles over the eastern US.  Finally, looks like some cold is on the way.  We will see where the EPS goes this afternoon.  

[John1122]

22 hours ago, jaxjagman said:

The western parts probably cringe over these maps.The Valley has so much diversity pertaining weather it's not even funny.Storm track is so crucial,someone unless it's a super storm is going to basically miss out.

I could be wrong but I seem to recall a full blown blizzard in W Tennessee/SWKY from a storm that ran across Alabama and up the Apps in the last couple of years.  

[John1122]

42 minutes ago, Carvers Gap said:

The 12z GFS...I know it is the GFS...hard not to like it.  Repeated shots if cold into a trough that buckles over the eastern US.  Finally, looks like some cold is on the way.  We will see where the EPS goes this afternoon.  

I'll be much more optimistic about the winter if we can get a cold November. Looks like the pattern is changing back towards what it in late summer/early fall. 

[Carvers Gap]

Winter-like temps showing on the 18z GFS centered just before and up to Halloween.  Need to get the rest of my sweet potatoes out of the ground.

[Carvers Gap]

The 12z EPS supports the cold shot from days 7-10.  And it is pretty cold.  From there (days 10-15), a +PNA ridge pops and a +NAO occurs.  We will see how the EPS works out those contradictory elements in future runs.

[John1122]

MRX working this in on Wednesday about 1000 feet above my elevation in CC.

 

A slight chance of snow showers before 9am, then a slight chance of rain showers. Partly sunny, with a high near 47. Chance of precipitation is 20%.

[Carvers Gap]

Looks like the first cold shot of the season rolls in w a step-down pattern through Halloween.  Then, as mentioned above, the contradictory teleconnections are beginning to sort themselves out for the 10-15 day time frame.  At the moment looks like slightly AN temps on the EPS for most of the forum area, but basically looks somewhat seasonal w the coldest temps in the lower 48 bottled up over the northern Rockies.  The cold lurks though.  

[nrgjeff]

Yes, it is a good track for them. However it is a heart breaker for me in CHA. Snow makes it to Signal Mountain, but Chattanooga proper only sees drizzle, lol!

20 hours ago, John1122 said:

I could be wrong but I seem to recall a full blown blizzard in W Tennessee/SWKY from a storm that ran across Alabama and up the Apps in the last couple of years.  

 

[Met1985]

16 hours ago, Carvers Gap said:

The 12z EPS supports the cold shot from days 7-10.  And it is pretty cold.  From there (days 10-15), a +PNA ridge pops and a +NAO occurs.  We will see how the EPS works out those contradictory elements in future runs.

I actually think the GFS has done a better job recently in the mid range with the way the troughs have been centered. I remember the weeklies last year where horrible in the mid to long range. 

[Carvers Gap]

1 hour ago, Met1985 said:

I actually think the GFS has done a better job recently in the mid range with the way the troughs have been centered. I remember the weeklies last year where horrible in the mid to long range. 

The Weeklies have a bias of being too warm and missing snaps.  As a whole though, they do pretty well if one keeps that in mind.  They also do pretty well at 500.  Last winter they correctly modelled warmth under what looked like a decent 500 pattern at times.   The GFS is good in spurts IMO.  If the pattern is slow and stable, it does ok.  If it is one where the pattern is variable or fast...it struggles.   I think the Weeklies have done pretty well w the northern hemisphere pattern, especially blocking, out to about 40 days.  They have done very well w the upcoming cold.   I still like the Euro suite better.  I think the physics of that model are just better.  Seems like the Weeklies did well w the seasonal summer that we just had.  Pretty good for a model that goes out to six  seven weeks IMO.

[Met1985]

Just now, Carvers Gap said:

The Weeklies have a bias of being too warm and missing snaps.  As a whole though, they do pretty well if one keeps that in mind.  They also do pretty well at 500.  Last winter they correctly modelled warmth under what looked like a decent 500 pattern at times.   The GFS is good in spurts IMO.  If the pattern is slow and stable, it does ok.  If it is one where the pattern is variable or fast...it struggles.   I think the Weeklies have done pretty well w the northern hemisphere pattern, especially blocking, out to about 40 days.  They have done very well w the upcoming cold.   I still like the Euro suite better.  I think the physics of that model are just better.

I must be thinking of something different because I remember the Weeklies showing a cold snap in the mid term forecast only to keep changing just about every time the weeklies come out. I remember it would show cold snaps for several runs only to go very warm the closer we got to the said time period. Personally I think the GFS has done a bit better recently with trough orientation recently with the mid range forecast. No doubt we will use every tool in our handbag again this year to see the future.

[Carvers Gap]

47 minutes ago, Met1985 said:

I must be thinking of something different because I remember the Weeklies showing a cold snap in the mid term forecast only to keep changing just about every time the weeklies come out. I remember it would show cold snaps for several runs only to go very warm the closer we got to the said time period. Personally I think the GFS has done a bit better recently with trough orientation recently with the mid range forecast. No doubt we will use every tool in our handbag again this year to see the future.

Yeah, I think you are right.  It wanted to flip cold and it just never happened...maybe in mid-late January of 2016?  It is not infallible by any means.  One winter, it tried to stay warm even though it was cold.  

[nrgjeff]

Weeklies are both pretty bad in the shoulder seasons. This year the choke jobs seemed to go well into June. However they did shape up for the balance of summer. Last winter had a couple fake-outs; otherwise, they did OK. Agree they miss little sub-patterns. Weeklies do best with the primary pattern.

[Carvers Gap]

Looks like the 12z EPS is leaning towards the cold staying over the northern Rockies.  Ridge over Alaska but a +NAO.  EPS puts a trough in neastern NA(north) but allows the SER to blunt any progression south of a third cold shot.

[Carvers Gap]

Pretty nice run of the Weeklies.  John, it likes a BN November.  The good thing is that they are not the only game in town as mid-range models now have some cold and high elevation snow potential...albeit light.   Will try to give a detailed look later.   

[Carvers Gap]

Would be much easier to explain w maps...but as Alaska goes, so does our weather.  If there is a ridge there, it is cold here.  If a trough, it is warm here.  The beginning of December features a trough returning.   Seems like the pattern modelled is one where cold loads out West for 2-4'weeks and then the jet buckles...and then it unloads into the Eastern US.  Let's see if that is not the eventual pattern.  With that idea (and yeah, it is waaay out there) it would suggest two decent time frames one around Christmas and early January and the other late January and early February.  Total speculation....let's see how it plays out.  Essentially, that is a continuation of the pattern that we are in now.  

[Daniel Boone]

I wonder how well QBO data is factored in in weeklies outlooks ? I bet little, if any.

[nrgjeff]

Carvers is on point. Looks to me like a dominant mild pattern with occasional cold intrusions. Well, occasional is better than none.

Euro weeklies keep BN through mid-November but I am skeptical past Veterans Day. SER tends to rebound faster than forecast on weeklies. However I have noticed cool staying power vs some op runs. Yet another Japan typhoon is forecast in 5 days. A full two-week cold regime would be a great accomplishment relative to the last 2-3 years. 

CFS keeps the cold going longer but I figure it is stuck. While the CFS has shown skill (or luck) with pattern changes, it has been horrible keeping them too long. I would still check the CFS for changes. Even if it is just luck, one should bet higher when your hand is hot.

QBO may be an advantage, it is certainly not bad. However, just like with La Nina, it will take more than -QBO to deliver cold into the Southeast. Look to leverage shorter patterns in conjunction with the QBO. Even outside typhoon season the MJO can assist.

[John1122]

It's somewhere in the forum but I will try to find the November cold = cold winters post. It was a very high probability of one leading to another. It would be big imo if we can pull off a cold November. If we can manage one that doesn't outright torch that would be much better than last year.

[Carvers Gap]

35 minutes ago, John1122 said:

It's somewhere in the forum but I will try to find the November cold = cold winters post. It was a very high probability of one leading to another. It would be big imo if we can pull off a cold November. If we can manage one that doesn't outright torch that would be much better than last year.

I think you are correct.  Just a cold cycle itself in November would put the next cold shot in the heart of winter if timing is normal...and the next shot in February.  Sometimes early December cold can create a thaw in midwinter...then it is debatable if winter return, basically a bookend winter,

I like these recurving typhoons.  When you get dealt a potentially crappy hand, reshuffling the deck is a good thing.   Those typhoons IMO really shake-up the pattern on this side of the globe.  Either way, this is 10x better than the torch of last fall, literally and figuratively.  

[Carvers Gap]

There have been some great winters where we had "just enough" cold at the right time.  Just no way to tell if the cold will get here w any moisture to work with.  Timing, as we all know, is key in the forum area.  95-96 is a decent example off the top of my head.  There was warmth that winter...but the right amount of cold for E TN to get a really good winter.  I am not calling for that type of winter.  But like Jeff said...better than last winter.

[Met1985]

2 hours ago, Carvers Gap said:

There have been some great winters where we had "just enough" cold at the right time.  Just no way to tell if the cold will get here w any moisture to work with.  Timing, as well know, is key in the forum area.  95-96 is a decent example off the top of my head.  There was warmth that winter...but the right amount of cold for E TN to get a really good winter.  I am not calling for that type of winter.  But like Jeff said...better than last winter.

 A lot of our best snowstorms have come with just enough cold at the right time. You have been around long enough to know there is nothing like a heavy wet snow right at 28 to 30 degrees that just plasters everything. I can also remember getting several big snows in December and in March just this way. That December 18th, 2009 storm was one for the record book. Down in my area they kept calling for just a few inches then turning to rain. The rain never happened. We ended up with 16 inches of snow the first storm then another 8 with the upslope machine taking effect.

[Carvers Gap]

52 minutes ago, Met1985 said:

 A lot of our best snowstorms have come with just enough cold at the right time. You have been around long enough to know there is nothing like a heavy wet snow right at 28 to 30 degrees that just plasters everything. I can also remember getting several big snows in December and in March just this way. That December 18th, 2009 storm was one for the record book. Down in my area they kept calling for just a few inches then turning to rain. The rain never happened. We ended up with 16 inches of snow the first storm then another 8 with the upslope machine taking effect.

Yep.  Even for our folks in northern MS and AL, they live in a world where they usually have barely enough...but they do get snow from time to time.  Obviously high latitude blocking is key most times but not all...the -QBO does lend some credence to the idea that we will have periods of blocking this winter, even if it does not lock in place.  

[Carvers Gap]

Looks like the models pulled a head fake for cold past d10 which is not surprising given the conflicted teleconnection look that they had a few days ago w a ridge over Alaska and BN heights over Greenland.  BN heights over Greenland are not a good look for prolonged cold.  Looks like cold followed by a big warm-up.  Who knows after that?

[nrgjeff]

Wow the CFS keeps getting warmer. Euro weeklies probably will follow tonight, based on Euro ensemble products. TS approaching Japan may barely make hurricane strength, which is not enough to shuffle the deck. So, dealer keeps getting 20-21 (10 or Ace up) and we keep getting 15-16.

Canada will have some very cold air, but no delivery to the US. Did the wall accidentally get built up there? Well, if we are going to have a trough west and ridge east, might as well get some severe weather going in November!