December 2018 Pattern And Forecast Discussion

[John1122]

Monthly November ranks through today. I'll look at some of these either later tonight or in a day or two and see how the winters right around them performed. But from what I've found so far, the theme of strongly cold periods that follow in winter will likely be much more common than AN winters.

Tri-Cities 19th coldest November.

Wise Va 20th coldest November.

Abingdon Va 11th coldest November.

Tazewell, Tn 7th coldest November.

Knoxville 13th coldest November.

Oak Ridge 2nd coldest November.

Chattanooga 10th coldest November.

Jackson Ky 4th coldest November.

London Ky 9th coldest November.

Crossville 5th coldest November.

Cookeville 5th coldest November.

Hunstville 10th coldest November.

Nashville 10th coldest November.

Clarksville 3rd coldest November.

Bowling Green 12th coldest November.

Jackson Tn 4th coldest November.

Memphis 6th coldest November.

[tnweathernut]

12 minutes ago, John1122 said:

Monthly November ranks through today. I'll look at some of these either later tonight or in a day or two and see how the winters right around them performed. But from what I've found so far, the theme of strongly cold periods that follow in winter will likely be much more common than AN winters.

 

John,

Thank you for all the work you put into this.  Sure looks like a big piece of the winter puzzle is a positive one.  

[Carvers Gap]

22 minutes ago, John1122 said:

Monthly November ranks through today. I'll look at some of these either later tonight or in a day or two and see how the winters right around them performed. But from what I've found so far, the theme of strongly cold periods that follow in winter will likely be much more common than AN winters.

Tri-Cities 19th coldest November.

Wise Va 20th coldest November.

Abingdon Va 11th coldest November.

Tazewell, Tn 7th coldest November.

Knoxville 13th coldest November.

Oak Ridge 2nd coldest November.

Chattanooga 10th coldest November.

Jackson Ky 4th coldest November.

London Ky 9th coldest November.

Crossville 5th coldest November.

Cookeville 5th coldest November.

Hunstville 10th coldest November.

Nashville 10th coldest November.

Clarksville 3rd coldest November.

Bowling Green 12th coldest November.

Jackson Tn 4th coldest November.

Memphis 6th coldest November.

Great job, John.  I second tnweathernut.

[BlunderStorm]

Wednesday looks pretty good for SWVA and parts of NETN on the  GFS 12z. It's seems pretty insistent over many runs but it seems like the other computer models aren't having it. A little later the clipper could drop some pocket change here on top of that but the low will probably be too north.

[Carvers Gap]

2 hours ago, BlunderStorm said:

Wednesday looks pretty good for SWVA and parts of NETN on the  GFS 12z. It's seems pretty insistent over many runs but it seems like the other computer models aren't having it. A little later the clipper could drop some pocket change here on top of that but the low will probably be too north.

Yeah, in this area...never sleep on those little systems that slide through.  A little upslope and they can put down and inch or two of snow on favorable mountains slopes.

[Carvers Gap]

The 18z GFS is a great example of what a parent high can do with a winter storm.  Verbatim, that is not snow here...but that would likely come north if real.  Having a parent hp show up is a nice feature that hasn't been there on the last few runs.  Still, long way to go.  

[jaxjagman]

We need the HP to be close to where the control shows plus the track is just important,once again a nice system this afternoons run with the a trowal,deformation band would be set up through the Valley .Once again another good look.Through 216 hr

[jaxjagman]

The more after looking at the temp profiles maybe we don't want this after all...lol..Big ZR threat.Yesterday the 850's were much better.

 

Edit:Some areas would be all snow.Some would be IP AND ZR mix,typical warm nose especially early into the season.Not that it matters right now anyways

[John1122]

The models are trending back in our favor for next weeks system with a long while to go. The Euro is a significant winter storm for the Plateau, SE KY, SWVA and NE Tennessee. 4-8 inches of heavy wet snow, would be even more if not for mixing issues. Shows a nice front end thump. The precip stays mixed over Eastern areas. The American models are very close themselves to getting it done for us. The Canadian is the oddest miller B I think I've ever seen. The low meanders around Mississippi for a while then transfers off the Savannah area.

The GFS is the Euro control but 150 miles Further north.

[Holston_River_Rambler]

I'll take my chances anytime with what the WPC is currently going with for day 7 (Dec. 8). About all you could ask for for our area, even if it ends up being barely too warm around Knoxville. 

 

 

 

[Carvers Gap]

Just for kicks and giggles, the 6z GEFS snow map is a nice one for NE TN.  At seven days out, this is going to bounce around all over the place.  Holston, that is a nice map.  Firstly, we want that hp to verify where it is over the Mid-West/eastern Plains.  Then, it would help if it was a bit stronger.  Its clockwise rotation of air would funnel cold down the west side of the Apps.  Anyone that knows my tendencies, knows that I always like slp over coastal eastern Louisiana w a track just inside Hatteras.  They have their benchmark for northern areas.  That is my benchmark for MBY....that and when the MA forum starts to follow one of these.  NE TN often gets some snow when DC does w this potential track.  I wish this storm was inside of four or five days.  

@jaxjagman, we want to no part of what was being kicked around yesterday.  Agree.  Established(old) cold air w over-running precip is not good.

  

[John1122]

GFS op was weird once again. The trailing high mostly fades and the storm sharply turns NNE briefly, it then gets shoved SE again by a H over the Carolinas or redevelops over Panama Florida. After it moves well out to sea, another low develops off the coast, possibly from another energy transfer from a system giving snow to East Tennessee. Strange looking progression. 

[John1122]

12z GFS loses the trailing high, cuts the storm, then sends it off the East Coast. Rainer for all, even Western NC outside of the higher peaks, which every other run of every other model is giving 10 inches or more. 

Canadian gives a nice dollop in Middle Tennessee, and crushes Western NC. 

I guess at this point I'm most amazed by how consistently the storm is showing up on all models. The details will continue to be wonky but models have gotten better at seeing storms very far out these days.

[BNAwx]

Other than this latest run of the GFS, it seems there's pretty good consensus (especially this far out) on the track of the low.  

What I'm wondering is if precip on the northern flank is being underdone on some of the modeling?  I've seen it happen before and I'm just wondering if that's a legitimate possibility.  

[BlunderStorm]

On the ICON as it begins to come into range it has the high ahead of the low. By the looks of it the high stays in place overtop of us on Saturday in the northern Ohio Valley but is gradually drifting east. The low looks nicely situated on the gulf coast with a defined center. Just speculating on how everything would interact it sort of looks like it would overrun us. I could see the high pressure perhaps keeping the storm south of some parts of our area in the NW but there isn't any mechanism to introduce colder air or keep the already situated cold air in place. I certainly agree with your all's assertion we want the high in the right place above all else. The storm in some form or fashion is seeming a given at this point. On the FV3 it seems to me it can't decide what to do with the storm. We end up with a broad area of low pressure with a center inland and another on the coast. The High in the plains is also accompanied by a high over the NE which delays the onset of the storm and brings relatively warmer air even further north than the last run. In prior runs the FV3 still has this but the high diminishes earlier. All in all confusing to wrap my head around and it's too far out to overthink it.  lol.

[Carvers Gap]

Probably not a bad idea to give the ensembles pretty heavy weight right now.  The 12z GEFS ensemble looked pretty similar to the past few runs.  We are so far out right now, that the operational runs are basically just an additional member of the ensemble if that makes sense...ie just one more possibility.  I suspect the actual interaction of the northern and southern streams is far from being accurately modeled.  I feel no better or worse than I did a couple of days ago.  What I hope is that this is a trend of storms taking the low road this winter....when we hit mid Jan, I want to see these lined-up for a couple of weeks.

[Carvers Gap]

52 minutes ago, BNAwx said:

Other than this latest run of the GFS, it seems there's pretty good consensus (especially this far out) on the track of the low.  

What I'm wondering is if precip on the northern flank is being underdone on some of the modeling?  I've seen it happen before and I'm just wondering if that's a legitimate possibility.  

BNAwx, great to see you in this thread.  Yeah, I would lean towards the slp taking the low road as well.  I wouldn't be surprised either to see some type of energy transfer though...seems like that has been a trend during the past few years.  Definitely want to get that high over the top.  

[John1122]

The Euro maintained a reasonably favorable set up for people from 40 and north. Translates to 4-8+ inches about 50 miles south of the Kentucky/VA border and points north all the way across the state. Looks like we're in for a week of model watching unless a definitive trend towards a cutter happens over the next few days. Biggest winners in our forum area that run Clarksville west to SWKY where a snow depth of 8-12 is snow, and east from Hancock County to just north of Johnson City with 8-12 depth showing up there. Impressive to get those numbers showing up on snow depth maps. Western Carolina foothlls get buried, 15+ widespread just east of the mountains.

As the precip arrives the northern forum areas have 850s of around -1 to -3c with ground temps around 31-33 degrees. So temps support a snow event. Big warm nose really hits the southern part of the forum. Never quite makes it to the far northern areas, some see 850s get to around 32-34 degrees with surface temps also remaining around the 32-34 range.  Euro shows moderate/heavy rain/snow over my area during this time and accumulation slows down, which is why areas west and east of me get 8-12 and I'm in the 4-6 range. Starts at around 162 hours for the region and lasts for around 24-30 hours.

[Holston_River_Rambler]

Anthony Masiello has a great thread on the twitterwebs today about this specific event (saw one section of it in the MA forum). I won't post the whole thing here since it is fairly long, but basically the gist is that he thinks the GFS/ FV3 is doing a really bad job handling the southern and norther stream separation and later interaction. It wants to have a slower (and trending slower) and deeper wave that ejects more amped and thus the cutters.  He favors the Euro for this specific event right now; faster and flatter wave thus the high is more favorable. Not a fan of flat and overrunning for me in Knoxville this time of year, would rather have amped AND south, but hopefully it translates to something nice for many others. 

Lot's can still change, but I were a fan of today's Euro run, he's someone I'd want to have in my pocket arguing in favor of that sort of a solution.

 Still a ways to go and for me, I'm just happy that several of the EPS members from 0z still got it done. 

[Holston_River_Rambler]

Check out the wonky changes with the energy in the Pacific at H5 over the past 6 runs of the GFS, as our wave is in N. Mexico/ CA/ Southwest depending on the run: https://imgur.com/a/umSzM2B 

The above would be for Friday evening, about the time the Euro has already ejected the energy. The earlier runs where the energy is over TX or NM resulted in more suppression and better timing with the High, like the Euro is showing. The Pacific energy seems to be effecting the ridging over top of the wave and how fast it ejects.

 

Euro has been bouncing around too, but notice the follow up energy in the Pacific (here denoted by the blue blob because Tropical Tidbits doesn't have the vorticity maps for the Euro) has been depicted in a pretty steady location over the past few runs (it only let me go back 5) or I would have done 6 too, like the GFS: https://imgur.com/a/XPr7lFX

UKMET is more like the Euro and I like that. It was one of the first to pick up on the big upper low that gave NW areas some snow earlier in Nov.  Doesn't mean it will be right here, but I sometimes think it strikes a nice balance between model camps. 

[AMZ8990]

https://weather.us/model-charts/euro/tennessee/m40_snow-depth-in/20181209-1200z.html

 

We could cash out with this look if that works for everybody around the state! Lol

[jaxjagman]

Why is it when winter storms are shown in the Valley they always seem to trend more north and when storms are more south of us they never trend north...lol

 

[Carvers Gap]

Have to say that the 12z EPS looks pretty decent. At least a 2" mean just south of I-40 for the length of the state.   Probably closer to 5"(edit) for NE TN and the Plateau. Something like 6-10" in the mountains.  Again, I sound like a broken record...really long way to go.  The track  is Louisiana to Hatteras w some individuals north of that.  Banana hp over the top.  I probably shouldn't be talking those types of details about a storm that far out, but that is a nice look.

[Carvers Gap]

A closer look does show plenty of individuals north of the mean track that I just mentioned.  So, that may not be as good a track as my post above had originally stated.  That is a signal that it has room to move north if just looking at this run verbatim.  

edit:  That said, it is so far out there that not all of the slp possibilities are likely to be picked up on this run.  

[Carvers Gap]

What a great write-up by MRX this evening...would rival some of the best detail in a discussion(link posted) that I have ever seen from them.  It closes with this little nugget.

https://forecast.weather.gov/product.php?site=MRX&issuedby=MRX&product=AFD&format=CI&version=1&glossary=1

The end of the extended has low confidence as southern stream energy
moves across the Southern Plains.  Behind this system, an increasing
amplitude ridge will move across the inter-mountain west with
another northern stream shortwave dropping out of Manitoba.  Do not
want to get into too much detail at this point but it is likely that
coastal cyclogenesis will occur with a surface low lifting northeast
depending on phasing of said systems.  GFS ensemble means do
indicate this potential during the weekend with sufficient moisture
advecting northward under upper level diffluence.  It is interesting
to also note that the latest GFS ensemble mean MSLP is in close
agreement with the latest deterministic ECMWF.  Placement of these
features will be crucial in how much precipitation we can receive
and any precip types.  Given that most global models have been
consistent on showing a system during this period will only use a
blend of models at this time, but it is likely to be an interesting
and quickly evolving extended period.

[TellicoWx]

Looking at each of the individual snow depth Euro Ens members, 12z took another step in the right direction. The pct of members has slowly been increasing the last 3 runs from around 20% to 40% for a significant winter storm in our area. Hopefully, the trend comtinues.

[AMZ8990]

36 minutes ago, TellicoWx said:

Looking at each of the individual snow depth Euro Ens members, 12z took another step in the right direction. The pct of members has slowly been increasing the last 3 runs from around 20% to 40% for a significant winter storm in our area. Hopefully, the trend comtinues.

Nice to have the EURO on board in some capacity.  Their are some big dogs in those 50 members too.  I’m interested in which options start to show consistency over the next few days.  It is pretty remarkable that all the models have a strong signal this far out, and the signal has been there for several days already to boot.

[John1122]

2 hours ago, jaxjagman said:

Why is it when winter storms are shown in the Valley they always seem to trend more north and when storms are more south of us they never trend north...lol

 

No kidding. We also see heavy snow in Arkansas, and the Carolinas on these storms but rain around here. 

[Bango]

Did the 0z Canadian jump to the gfs? (Not good)

[Wurbus]

11 minutes ago, Bango said:

Did the 0z Canadian jump to the gfs? (Not good)

The low cuts on the CMC. The low went from off the Georgia coast at 192 on the 12z to western Kentucky at 180.