December 2020 Medium/Long Term Pattern Discussion.

[Carvers Gap]

WxBell algorithm.  About as marginal as one could get.  SLP is slightly NW of 0z. If it goes like the other system...will trend NW a few more runs and then jog SE quite a bit and back a tick NW.

[tnweathernut]

Weak (Miller A) system to our southeast with a robust moisture field is my favorite setup for snow.  
 

Usually mutes the dreaded warm nose, and in this particular case with temps about as marginal as they come .....would likely be the best case scenario providing the best chance at something other than rain for the elevated and far eastern areas.

[John1122]

The NAM rolled in guns blazing for the West and Mid Valley. Fizzles for the East Valley. 

[John1122]

RGEM is slower/warmer than the NAM. On the NAM the Northern stream wave gets out in front of the southern system. On the RGEM the northern wave is more in synch and is sitting in the great Lakes when the storm is getting going. That shuts down some of the cold for the system on the RGEM so it's a rainer.

[John1122]

The ICON has a 1 to 2.5 inch event basically for some of middle to the Plateau. Doesn't really hit the far Western areas like the NAM did. 

[John1122]

GFS is slowly working it's way more towards the more snowy models. 12z today it bad virtually nothing in the mountains. 00z it buries the mountains with 6-10 inches. Bigger and longer lasting precip shield in general too. 

[John1122]

Too warm on the Euro this run on wave 1. Jamestown gets some heavy mix. The rest of us stay liquid. 

[John1122]

Wave 2 is weaker and further north. 

[weathertree4u]

6 hours ago, John1122 said:

The NAM rolled in guns blazing for the West and Mid Valley. Fizzles for the East Valley. 

Lock it in!

[John1122]

Overnight modeling is all too wound up/further north. Very cold rain with snow above 2500-3000 feet.  Need everything a good 100 to 150 miles south but there's not much to force it down and cold is extremely marginal. 

[Holston_River_Rambler]

MRX giving us some hope this AM @John1122

 "Midlevel frontogenesis ramps up between 06Z and 12Z,
and QPF during this time frame are expected to be in the half to one
inch range. The tricky part is how quickly temperatures will fall.
The models may be underestimating the cooling that may ensue as the
frontogenesis ramps up, so the forecast will knock down NBM temps a
little Sunday night. This will put snow in the mountains of East TN,
SW VA, and parts of the northern Cumberland Plateau. If the cooling
occurs even faster, then there could be a potential for significant
snow amounts in the mountains, but confidence remains low at this
time."

 

verbatim the RGEM has some very heavy precip from that forcing:

Forcing:

 

Precip:

If I had a vehicle that could handle the drive in a big snow, I'd be thinking about chasing to High Knob for this one. 

[Carvers Gap]

Not a fan of where the 0z EPS went last night in the LR.  I really hate playing the "low gets stuck in the SW" game with that model.  Huge bias, but sometimes it is right.  Most other modeling looks good in the LR, but EPS makes me a bit nervous.

As for the Monday system, same playbook as the last system on almost all modeling, and I am not sure why that happens - massive NW shift.  Now, lets' see if it doesn't start coming back SE later tonight and tomorrow.  If we get snow, looks like the Plateau would be the spot.  NE TN is out of this one unless it goes eastward - and I am not ruling that out.

[Carvers Gap]

On a positive note, the CFSv2 Seasonal(not the CFS extended) this morning flipped cold for January.  No idea if that holds in future runs as it bounces around, but it has been solid in the warm camp for January for some time.  One thing to watch for is that the GEPS has shifted (around Christmas) the AN height field into Nova Scotia vs Greenland - looks temporary but that would pump an EC ridge if true.  Again, I really don't like losing the EPS in the LR as it has reverted back to its original warm solution along the EC around Dec 21 which is just three days later than the steadfast runs of the week before(never ending warm).  And again, it is holding a low in the Southwest which is often a miserable error that it often repeats.  American modeling is colder(surprise!) while other modeling has backed-off the nice 500 pattern in varying degrees after the 20th.  Could just be a wobble...time will tell.  Last winter has me gun shy.  

[Carvers Gap]

Thought I might take some time to look at why we are seeing some variability in modeling in the long range this morning.  Grabbed the CA OLR map (outgoing long wave radiation).  The cooler areas on the map indicate higher cloud tops and signal more convection(t-storms).  The first image is the CA(constructed analog) OLR map.  You can see the IO (Indian Ocean) go very quiet as the wave propogates(moves) from the MC to the dateline.  As a quick note, the MJO's favorable phases for winter weather are near the dateline(180).  So, days 11-15 would see the MJO move into phase 7(and maybe even 8,1) which is colder in NDJ (DJF is warm).  So, the phase 7 is sort of in-between the DJF and NDJ  by late month, and that causes a washed out signal since one three month analog is warm(DJF) and the other is cooler (NDJ).  The second map is from the GEFS.  The OLR there is locked into the MC(Maritime Continent) for the foreseeable future.  How modeling is handling the Indian Ocean and the MC is not consistent among different models IMHO.  Some models are taking the MJO through 4 to 5 to 6 and one would guess...7.  The EMON rotates through the circle of death.  The CA rotates at higher amplitude to 7.  The GEFS stalls the MJO.  In other words, models are all over the place with the MJO.  Take one look at the 500 maps for the major ensembles this AM, and you will see the model spread.

 

 

   

 

All of that said, we "might" see a more conducive Pacific later this month or even by January.  As I noted yesterday, if we can use the -NAO to bridge to the a better Pacific set-up later on...we might have a chance to stay seasonal(or slightly above) until the next legit cold shot - and that is a win if we like winter.  Why?  Normal or even slightly above will get the job done later this month.   Right now, I don't think I buy much after d15 - cold or warm.  I would say my confidence level is low.  If forced, I would say we will continue to see weaker heights over the SE for the foreseeable future with some ridges rolling through.  I do think there is a chance (if the -NAO verifies and we get even a temporary PNA or EPO) that we could see some colder temps rotate through.  I think the problem right now is the Atlantic block is muting what would otherwise be a total torch.  Computer models, like humans, are trying to figure out how much of an influence that block is going to have.  At the very least, we are going to likely see an active and stormy patterns with cutters and some Miller A(with marginal cold...increasingly colder as December averages take hold) stuff.  

References:

https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml  (CA stuff)

https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/Composites/Temperature/ (phase correlation map of MJO to NA wx per three month increments)

https://www.climate.gov/news-features/blogs/enso/what-mjo-and-why-do-we-care (phases of MJO by longitude)

https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/clivar_wh.shtml (various model output for the MJO)

[Carvers Gap]

And to quote a famous poster of the TN Valley..."When we start talking about the MJO, that is usually not a good sign."  

[nrgjeff]

LOL Carvers! When gas traders starting talking about the MJO, money is about to be lost.

First the bad news. Boundary layer BL remains a disaster at lower elevations. Just too warm.

Good news is the -NAO is pretty consistent. A little retrograde would get the job done for higher elevations like the Plateau and Mountains.

Agree with @tnweathernut above a weak Miller A is better, esp this warm BL environment. At least higher elevations could get it.

This isn't November or late Feb. Looks like a decent pattern for late December into the New Year.

[Daniel Boone]

48 minutes ago, Carvers Gap said:

Thought I might take some time to look at why we are seeing some variability in modeling in the long range this morning.  Grabbed the CA OLR map (outgoing long wave radiation).  The cooler areas on the map indicate higher cloud tops and signal more convection(t-storms).  The first image is the CA(constructed analog) OLR map.  You can see the IO (Indian Ocean) go very quiet as the wave propogates(moves) from the MC to the dateline.  As a quick note, the MJO's favorable phases for winter weather are near the dateline(180).  So, days 11-15 would see the MJO move into phase 7(and maybe even 8,1) which is colder in NDJ (DJF is warm).  So, the phase 7 is sort of in-between the DJF and NDJ  by late month, and that causes a washed out signal since one three month analog is warm(DJF) and the other is cooler (NDJ).  The second map is from the GEFS.  The OLR there is locked into the MC(Maritime Continent) for the foreseeable future.  How modeling is handling the Indian Ocean and the MC is not consistent among different models IMHO.  Some models are taking the MJO through 4 to 5 to 6 and one would guess...7.  The EMON rotates through the circle of death.  The CA rotates at higher amplitude to 7.  The GEFS stalls the MJO.  In other words, models are all over the place with the MJO.  Take one look at the 500 maps for the major ensembles this AM, and you will see the model spread.

 

 

   

 

All of that said, we "might" see a more conducive Pacific later this month or even by January.  As I noted yesterday, if we can use the -NAO to bridge to the a better Pacific set-up later on...we might have a chance to stay seasonal(or slightly above) until the next legit cold shot - and that is a win if we like winter.  Why?  Normal or even slightly above will get the job done later this month.   Right now, I don't think I buy much after d15 - cold or warm.  I would say my confidence level is low.  If forced, I would say we will continue to see weaker heights over the SE for the foreseeable future with some ridges rolling through.  I do think there is a chance (if the -NAO verifies and we get even a temporary PNA or EPO) that we could see some colder temps rotate through.  I think the problem right now is the Atlantic block is muting what would otherwise be a total torch.  Computer models, like humans, are trying to figure out how much of an influence that block is going to have.  At the very least, we are going to likely see an active and stormy patterns with cutters and some Miller A(with marginal cold...increasingly colder as December averages take hold) stuff.  

References:

https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjo.shtml  (CA stuff)

https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/Composites/Temperature/ (phase correlation map of MJO to NA wx per three month increments)

https://www.climate.gov/news-features/blogs/enso/what-mjo-and-why-do-we-care (phases of MJO by longitude)

https://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/clivar_wh.shtml (various model output for the MJO)

Excellent interpretation and explanation Carver!! Logically laid out reasoning.

[Carvers Gap]

The 12z CMC is close to a big storm for Weds in this area...very big for MA and NE.  

[tnweathernut]

1 hour ago, Carvers Gap said:

The 12z CMC is close to a big storm for Weds in this area...very big for MA and NE.  

12z Euro also very close to a big storm for northeast TN and is a big storm for the NC mountains, SW Va and points northeast......

[Holston_River_Rambler]

Here's the 12z EPS for you NE TN and SW VA folks. I hope it hits y'all with a good one!

 

 

 

 

 

 

[Carvers Gap]

Not sure if it is the WxBell algorithm, but it has snow for the first system over SE KE, the Plateau of TN, and SW VA, and the Smokies.  2-3" of snow on the Plateau. 

[John1122]

The Euro is back to me getting 2 or 3 inches Monday. It's going to be razor thin for a lot of us next week. 

[Carvers Gap]

12z EPS much better looking this run d10+ with a small PNA ridge and NAO block.  We can live with that.

[John1122]

Looks like the 18z American models are having issues. My friend has a few acres for sale at 2900 feet. So tempted to move but I'd have to sacrifice things like reliable internet and you know, build a new house plus convince my family moving to fulfill my snow obsession is a good idea when I can drive to 2900 feet in 5 minutes or so. It would probably double my snowfall yearly though. That extra 1200 feet makes a huge difference. I think that area here will probably get several inches of snow out of one or both systems next week. I believe the snow level was down to 2660 feet on a sounding I looked at that showed rain here during the overnight runs. I don't think there's any private land above 3000 feet here anywhere. The government owns it all in some form or another be it WMA, State Park or the Air Force I think owning the 3500+ land on Cross Mountain.  The top there averages about 55 inches of snow a year.

[Daniel Boone]

1 hour ago, John1122 said:

Looks like the 18z American models are having issues. My friend has a few acres for sale at 2900 feet. So tempted to move but I'd have to sacrifice things like reliable internet and you know, build a new house plus convince my family moving to fulfill my snow obsession is a good idea when I can drive to 2900 feet in 5 minutes or so. It would probably double my snowfall yearly though. That extra 1200 feet makes a huge difference. I think that area here will probably get several inches of snow out of one or both systems next week. I believe the snow level was down to 2660 feet on a sounding I looked at that showed rain here during the overnight runs. I don't think there's any private land above 3000 feet here anywhere. The government owns it all in some form or another be it WMA, State Park or the Air Force I think owning the 3500+ land on Cross Mountain.  The top there averages about 55 inches of snow a year.

Would be nice to have a home on High Knob in Wise County. Back in the early 2000s Dave Dierks Chief Meteorologist on WCYB said the average there was 110 inches a Season. He listed the Ski Resort areas in NC and their average was 90 to 100". 

       Highknoblandform.com has alot of info. About the area.

[Daniel Boone]

2 hours ago, Carvers Gap said:

12z EPS much better looking this run d10+ with a small PNA ridge and NAO block.  We can live with that.

Of course CPC bought the mild runs and ran with them in their 8-14 day.

[Daniel Boone]

Thought some of you all may find this interesting.  This is from the University of Virginia's Climate office. Wise holds the States official Seasonal Snowfall Record. 124.2 inches in 1995-96. I lived in Pennington gap, Lee County then and recorded 52" .

        

     Virginia Extremes:
 

Highest Sea-level Pressure	1051.2mb	January 31, 1981	Washington National
Lowest Sea-level Pressure	965.3mb	March 15, 1993	Richmond
Highest Wind Speed	134mph	September 14, 1944	Cape Henry
Highest Temperature	110F	July 15, 1954	Balcony Falls1
Lowest Temperature	-30F	January 21, 1985	Mountain Lake Biological Station
High 24-hour Precipitation	27.35 in	August 20, 1969	Nelson County2
High Monthly Precipitation	24.98 in	June, 1995	Glasgow3
High Annual Precipitation	81.78 in	1972	Montebello
Least Annual Precipitation	12.52 in	1941	Moore's Creek
Greatest 24-hour Snowfall	33.0 in	March 6, 1962	Big Meadows
High Single Storm Snowfall	48.0 in	January 6-7, 1996	Big Meadows4
Greatest Monthly Snowfall	54.0 in	February, 1899	Warrenton
Greatest Seasonal Snowfall	124.2 in	1995-6	Wise5

[Holston_River_Rambler]

Kinda diggin' that the Euro is digging the energy for the second storm even more than 12z, at 18z:

 

Further south and a stronger high press seems to have been the trend with that one lately, though not sure how long that will continue. 

 

[Carvers Gap]

Starting to become more of the opinion that we are going to need another strong cold shot of air into our region.  Marginal systems at this time of year at lower elevations and at this latitude are just tough to get much mojo from.  That said, within the next two weeks, we get to much more favorable climatological norms, and that helps.  

[John1122]

23 minutes ago, Carvers Gap said:

Starting to become more of the opinion that we are going to need another strong cold shot of air into our region.  Marginal systems at this time of year at lower elevations and at this latitude are just tough to get much mojo from.  That said, within the next two weeks, we get to much more favorable climatological norms, and that helps.  

The 12z Euro looked like an early December 2009 paste job here that put down 8 inches of heavy wet cement overhead while it rained north, south, east and west of here. For whatever reason this county was just in the perfect spot in the storm and it dropped silver dollars for 5 straight hours. It was mixed slush about 15 miles away in Scott and Whitley County Kentucky but just hammered here.