Winter 2015-16

[Carvers Gap]

These teleconnections are pretty amazing...I am not sure I have seen them looking this good and in sync.  Too much of a good thing?  Who knows?  But pretty amazing.   Would seem to signal cold and storminess for the duration of those CPC ensembles.  But as Jeff stated, there is a flipside to this coin.  I think we should have a trough in the East through Feb...but there is more than one viewpoint on this.  And I am not a met.  So, take it for what it is worth. 

 

 

 

[tnweathernut]

The 12z GEFS has a pretty good look for some wintry fun around day 6, and again around day 10ish. (maybe even a clipper between days 6 and 10). Those are two time periods we have been watching and I am guessing will continue to watch!

[Stovepipe]

The 12z GEFS has a pretty good look for some wintry fun around day 6, and again around day 10ish. (maybe even a clipper between days 6 and 10). Those are two time periods we have been watching and I am guessing will continue to watch!

 

Parallel EPS is still suggesting action around day 10 as well.

[tnweathernut]

Parallel EPS is still suggesting action around day 10 as well.

I am not ready to sleep on Monday/Tuesday just yet.  Return flow comes back pretty quickly after our Sunday front blows through.  Will be interesting to see if a light event can sneak in on someone in the TN Valley region.

[Carvers Gap]

12z Euro w/ a big Lakes cutter.  Super similar to the UKMET this AM.  Still will watch for a few more runs.  Seems to drag that energy across the SW pretty slow...  Really impacts the wx beyond that time frame.  Until the models lock down the Fri-Sat solution....everything modeled after that time frame has to be taken w/ a grain of salt.  The Euro is suspiciously tranquil after that.  But if that cutter deepens over the Lakes, suppression might be the story.  Somehow, I doubt it. 

[Carvers Gap]

Just waiting for the rest of the Euro to come on board...@ 228 looks like the NAO restrengthens, the PNA ridge is still stall, and more cold air coming south out of the Plains in Canada...will edit this post in a few minutes w/ my final thoughts on the 12z Euro.

 

edit:  Bout all I can get from this.  The 12z appears to be holding back energy late in its run as well as popping a very strong -NAO.  Split flow is apparent but the energy underneath doesn't sync with the energy dropping out of the north.  You have heard it since we began this new pattern..plenty of potential in run.  The PNA weakens but is still present.  Cold pinwheels southeast in repeated shots of cold throughout the run to h240.  Again, the biggest feature in this 12z Euro is the stout NAO...

[Carvers Gap]

12z Canadian is similar with this weekend's system.  The difference with this is that it cuts the low up through the middle TN.  Both the Euro and Canadian look very similar taking a strong low into the Lakes.  Whether that low can help form a 50/50 low is important.  Also, just how far does the associated cold air push after that storm?  Does it drape over the south giving energy a chance to ride along it or does it push all of the way to the GOM?  Important questions.  The Canadian also had a strong -NAO late in the run but appeared more east based. 

 

My biggest takeaway this afternoon...the models still seem to be struggling with the strong blocking at high latitudes.  

 

edit:  EPS rolling...let's see what it holds.

[Carvers Gap]

Check out that block at h144 on the 12z UKMET...courtesy of Meteocentre.

 

[Silas Lang]

Pardon my ignorance, but on the 12z GFS, between hours 132-150, could that be a potential over running event if cold air sticks around? Storm in the gulf looks as if some moisture could make it to the eastern valley, especially around hour 150. Temps at 850 good for snow falling, but surface is too warm for any accumulation by the time most of the moisture gets there. Is this the potential Jeff was talking about yesterday? Also, one more question: are typical over running events when we see storms (from the gulf) with snow that shoot a finger of moisture up the spine of the apps? Just asking because I seem to remember getting a surprise few inches from a setup like this a couple of years ago. The moisture just somehow seemed to stretch out from the gulf. Don't the models sometimes under represent gulf moisture?

[jaxjagman]

Pardon my ignorance, but on the 12z GFS, between hours 132-150, could that be a potential over running event if cold air sticks around? Storm in the gulf looks as if some moisture could make it to the eastern valley, especially around hour 150. Temps at 850 good for snow falling, but surface is too warm for any accumulation by the time most of the moisture gets there. Is this the potential Jeff was talking about yesterday? Also, one more question: are typical over running events when we see storms (from the gulf) with snow that shoot a finger of moisture up the spine of the apps? Just asking because I seem to remember getting a surprise few inches from a setup like this a couple of years ago. The moisture just somehow seemed to stretch out from the gulf. Don't the models sometimes under represent gulf moisture?

Looks like a front with moisture ahead of it

[jaxjagman]

Usually when there is a strong -AO/NAO the bird goes to us.Systems generally go through SE Ga or N/FL just about like the EPS showed today it's very rare anything makes it here with that path.The southern parts might get something,not us.

 

Edit:I'm generally talking about us in the middle

[Greyhound]

edit:  Bout all I can get from this.  The 12z appears to be holding back energy late in its run as well as popping a very strong -NAO.  Split flow is apparent but the energy underneath doesn't sync with the energy dropping out of the north.  You have heard it since we began this new pattern..plenty of potential in run.  The PNA weakens but is still present.  Cold pinwheels southeast in repeated shots of cold throughout the run to h240.  Again, the biggest feature in this 12z Euro is the stout NAO...

 

I'm terrible with reading models, and don't have access to Euro data, but isn't holding energy back one of the known biases of the Euro mdel?  If so...could there be a possibility for those two streams to merge? 

[1234snow]

Pardon my ignorance, but on the 12z GFS, between hours 132-150, could that be a potential over running event if cold air sticks around? Storm in the gulf looks as if some moisture could make it to the eastern valley, especially around hour 150. Temps at 850 good for snow falling, but surface is too warm for any accumulation by the time most of the moisture gets there. Is this the potential Jeff was talking about yesterday? Also, one more question: are typical over running events when we see storms (from the gulf) with snow that shoot a finger of moisture up the spine of the apps? Just asking because I seem to remember getting a surprise few inches from a setup like this a couple of years ago. The moisture just somehow seemed to stretch out from the gulf. Don't the models sometimes under represent gulf moisture?

I'm really interested in this time frame you are talking about. The 11-13th of early next week. It looked really close on the 12z GFS.

[Carvers Gap]

I'm terrible with reading models, and don't have access to Euro data, but isn't holding energy back one of the known biases of the Euro mdel? If so...could there be a possibility for those two streams to merge?

That would be my thinking. When I see energy get dumped (and it is late in the run so prob will change anyway) into the Southwest...have to be careful of the run from that point onward. That is a known bias. But they have had a big storm there this winter already. So, sometimes it is not a bias. When I animated the pattern, it seemed to hang back. Not sure it it helps us either way. But it might be an error.

[Carvers Gap]

Pardon my ignorance, but on the 12z GFS, between hours 132-150, could that be a potential over running event if cold air sticks around? Storm in the gulf looks as if some moisture could make it to the eastern valley, especially around hour 150. Temps at 850 good for snow falling, but surface is too warm for any accumulation by the time most of the moisture gets there. Is this the potential Jeff was talking about yesterday? Also, one more question: are typical over running events when we see storms (from the gulf) with snow that shoot a finger of moisture up the spine of the apps? Just asking because I seem to remember getting a surprise few inches from a setup like this a couple of years ago. The moisture just somehow seemed to stretch out from the gulf. Don't the models sometimes under represent gulf moisture?

Definitely has some potential as you and 1234 mentioned. I think I had that in my response to Jax earlier. But the 12z GFS does spin up a storm for 12-13th. A bit too far south and east...but man, all of that can and probably will change on subsequent runs. 12z GEFS per a buddy mentioned it had a strong signal at six days. I haven't found a ton of support on other models for it - yet . Also, I can't remember if that is the same piece of energy that I was eyeballing around the 11th. It is possible that is the piece right after it. We will need to watch how strong that low is that cuts to the Lakes preceding that energy. Too strong and it is suppression city. Models are all over the place in regards to specifics past 84 hours.

Edit: Typos fixed. Just wait until you are over 40 typing on an iPhone. It looks great...until you look more closely.

[jaxjagman]

NATIONAL WEATHER SERVICE NASHVILLE TN
135 PM CST WED JAN 6 2016

.DISCUSSION...

HIGH PRESSURE CENTERED TO OUR NORTHEAST CONTINUES TO DOMINATE THE
WEATHER ACROSS MIDDLE TENNESSEE THIS AFTERNOON, WITH RETURN FLOW
ADVECTING SLIGHTLY WARMER AIR THIS WAY AND CIRRUS CLOUDS STREAMING
IN AHEAD OF TOMORROW EVENING`S SHORTWAVE PASSAGE. LOOK FOR
TEMPERATURES TO CONTINUE WARMING THROUGH THE END OF THE WEEK, EVEN
AS AN UPPER TROUGH SWINGS THROUGH THE MID STATE THURSDAY EVENING
AND BRINGS A BAND OF SHOWERS ACROSS THE AREA. THIS WILL BE A HIGH
POP/LOW QPF EVENT, WITH NO AIR MASS CHANGE AS WE WILL REMAIN IN
THE MARITIME TROPICAL SECTOR OF A MUCH LARGER, SYNOPTIC-SCALE
FRONTAL SYSTEM THAT WILL AFFECT MIDDLE TENNESSEE THIS WEEKEND. A
STRENGTHENING SURFACE LOW WILL RACE FROM THE SOUTHERN PLAINS INTO
THE GREAT LAKES FROM 00Z SATURDAY TO 12Z SUNDAY, WITH A COLD FRONT
PUSHING THROUGH MIDDLE TENNESSEE ON SATURDAY AND MUCH COLDER AIR
DROPPING DOWN BEHIND THE FRONT. AT THIS TIME, THE MODEL SOUNDINGS
ARE SHOWING NO INSTABILITY WITH THIS SYSTEM, SO WE`LL PROBABLY
LEAVE THUNDER OUT OF SATURDAY`S FORECAST. THIS COULD OBVIOUSLY
CHANGE, BUT AT THIS TIME THUNDER SEEMS UNLIKELY. AT ANY RATE, THE
PRIMARY SHORTWAVE WILL COME THROUGH A FEW HOURS BEHIND THE FRONT
ALONG WITH A SWATH OF LOW-LEVEL OCCLUDED FRONT MOISTURE. WE CAN
EXPECT FLURRIES OR LIGHT SNOW WITH THIS WRAP-AROUND MOISTURE,
GIVEN THE STRENGTH OF THE COLD ADVECTION SATURDAY NIGHT AND
SUNDAY. THERE IS SOME DISCREPANCY BETWEEN THE ECMWF AND GFS MODELS
REGARDING THE STRENGTH AND PLACEMENT OF THE SURFACE LOW, WITH THE
ECMWF DEEPENING THE LOW CONSIDERABLY MORE AND BRINGING IT MUCH
CLOSER TO MIDDLE TENNESSEE THAN THE GFS. IF THE ECMWF PROVES
CORRECT, IT COULD RESULT IN MEASURABLE SNOWFALL FOR MIDDLE
TENNESSEE ON SUNDAY, GIVEN THE MUCH DEEPER WRAP-AROUND MOISTURE
AND BETTER DYNAMICS. AT THIS POINT, HOWEVER, WE`LL LEAVE
ACCUMULATIONS OUT OF THE FORECAST.

[jaxjagman]

Check out that block at h144 on the 12z UKMET...courtesy of Meteocentre.

 

ukmet block.JPG

Me likey this,stronger than the euro even but same placement

[Carvers Gap]

Me likey this,stronger than the euro even but same placement

Probably need an eastward trend and send that up the eastern Valley for optimimum results. Post the Canadian for that time frame...global.

[John1122]

Usually when there is a strong -AO/NAO the bird goes to us.Systems generally go through SE Ga or N/FL just about like the EPS showed today it's very rare anything makes it here with that path.The southern parts might get something,not us.

 

Edit:I'm generally talking about us in the middle

Actually, during strong Nino's Nashville's snow is 300 percent higher with a -ao/nao than without.

[Carvers Gap]

NATIONAL WEATHER SERVICE NASHVILLE TN

135 PM CST WED JAN 6 2016

.DISCUSSION...

HIGH PRESSURE CENTERED TO OUR NORTHEAST CONTINUES TO DOMINATE THE

WEATHER ACROSS MIDDLE TENNESSEE THIS AFTERNOON, WITH RETURN FLOW

ADVECTING SLIGHTLY WARMER AIR THIS WAY AND CIRRUS CLOUDS STREAMING

IN AHEAD OF TOMORROW EVENING`S SHORTWAVE PASSAGE. LOOK FOR

TEMPERATURES TO CONTINUE WARMING THROUGH THE END OF THE WEEK, EVEN

AS AN UPPER TROUGH SWINGS THROUGH THE MID STATE THURSDAY EVENING

AND BRINGS A BAND OF SHOWERS ACROSS THE AREA. THIS WILL BE A HIGH

POP/LOW QPF EVENT, WITH NO AIR MASS CHANGE AS WE WILL REMAIN IN

THE MARITIME TROPICAL SECTOR OF A MUCH LARGER, SYNOPTIC-SCALE

FRONTAL SYSTEM THAT WILL AFFECT MIDDLE TENNESSEE THIS WEEKEND. A

STRENGTHENING SURFACE LOW WILL RACE FROM THE SOUTHERN PLAINS INTO

THE GREAT LAKES FROM 00Z SATURDAY TO 12Z SUNDAY, WITH A COLD FRONT

PUSHING THROUGH MIDDLE TENNESSEE ON SATURDAY AND MUCH COLDER AIR

DROPPING DOWN BEHIND THE FRONT. AT THIS TIME, THE MODEL SOUNDINGS

ARE SHOWING NO INSTABILITY WITH THIS SYSTEM, SO WE`LL PROBABLY

LEAVE THUNDER OUT OF SATURDAY`S FORECAST. THIS COULD OBVIOUSLY

CHANGE, BUT AT THIS TIME THUNDER SEEMS UNLIKELY. AT ANY RATE, THE

PRIMARY SHORTWAVE WILL COME THROUGH A FEW HOURS BEHIND THE FRONT

ALONG WITH A SWATH OF LOW-LEVEL OCCLUDED FRONT MOISTURE. WE CAN

EXPECT FLURRIES OR LIGHT SNOW WITH THIS WRAP-AROUND MOISTURE,

GIVEN THE STRENGTH OF THE COLD ADVECTION SATURDAY NIGHT AND

SUNDAY. THERE IS SOME DISCREPANCY BETWEEN THE ECMWF AND GFS MODELS

REGARDING THE STRENGTH AND PLACEMENT OF THE SURFACE LOW, WITH THE

ECMWF DEEPENING THE LOW CONSIDERABLY MORE AND BRINGING IT MUCH

CLOSER TO MIDDLE TENNESSEE THAN THE GFS. IF THE ECMWF PROVES

CORRECT, IT COULD RESULT IN MEASURABLE SNOWFALL FOR MIDDLE

TENNESSEE ON SUNDAY, GIVEN THE MUCH DEEPER WRAP-AROUND MOISTURE

AND BETTER DYNAMICS. AT THIS POINT, HOWEVER, WE`LL LEAVE

ACCUMULATIONS OUT OF THE FORECAST.

Glad to see some discussion on that! Good catch. Still a bit of a stretch, but hey...things prob will change slightly over the next few runs.

[jaxjagman]

Actually, during strong Nino's Nashville's snow is 300 percent higher with a -ao/nao than without.

Yeah but that would depend on a east or west NAO,should have mentioned that,sure looks east right now

[jaxjagman]

EPS looks active though on 16,system off Fl,system coming off Texas kooks to be going NNE OR NE at the same time frame

[Carvers Gap]

EPS looks active though on 16,system off Fl,system coming off Texas kooks to be going NNE OR NE at the same time frame

As DT states, get the pattern and then the event.  I have stated ad nauseam that I like the pattern.  So have others.  Time will tell if it actually pays-off.  Plenty of other perspectives to keep things balanced.  Hopefully, somebody in this region can score some winter wx!

[Stovepipe]

Might be such a thing as too much blocking if Mexico starts getting our snow lol.  Still I'll take my chances with the teleconnections we're seeing modeled for the medium and long term.  Just need something we can sink our teeth into.  Might have to play the long game on this one, which is not terribly surprising considering it's a Nino year.

[Carvers Gap]

Yeah but that would depend on a east or west NAO,should have mentioned that,sure looks east right now

As Bob Chill said...the 12z has been kind to us...maybe also said he would marry that run if he could!!! And I agree, that NAO on the Euro was about perfect. So, we will see if it holds. Good signs for sure, but keepin' it level. Also, definitely worth keeping an eye on the potential blizzard heading to the Detroit area this weekend. Not trying to hype...but the middle and west parts of the forum could see some light snow(See Jax's post out of Nashville). Heck, if it spins up...could see an upslope event here. Just have to see how tomorrow's models roll.

[Carvers Gap]

Might be such a thing as too much blocking if Mexico starts getting our snow lol. Still I'll take my chances with the teleconnections we're seeing modeled for the medium and long term. Just need something we can sink our teeth into. Might have to play the long game on this one, which is not terribly surprising considering it's a Nino year.

Talked to tnweathernut today, and he has some good stats on the blocking in 97-98. So, sure blocking does not always work out. John and TN both called for a great second half. So, they look better with each run. I am like you, give me that strong high latitude blocking for my starting line-up. I am decently excited about the next month or so. But still a part of me that needs to see it to believe it.

[nrgjeff]

Good questions:

Pardon my ignorance, but on the 12z GFS, between hours 132-150, could that be a potential over running event if cold air sticks around? Storm in the gulf looks as if some moisture could make it to the eastern valley, especially around hour 150. Temps at 850 good for snow falling, but surface is too warm for any accumulation by the time most of the moisture gets there. Is this the potential Jeff was talking about yesterday?

 

Also, one more question: are typical over running events when we see storms (from the gulf) with snow that shoot a finger of moisture up the spine of the apps? Just asking because I seem to remember getting a surprise few inches from a setup like this a couple of years ago. The moisture just somehow seemed to stretch out from the gulf. Don't the models sometimes under represent gulf moisture?

 

First, the streamer of moisture appears to be ahead of a northern stream system (front). It is not exactly what I'm looking for, esp if the northerner drags the 850 line north. Could also be post-frontal snow showers. Southern stream system is shown buried to our south on a few models at close to the same time. I would like that one, or another like it, to come out a little farther north. The moisture sought would come from it and look more like a precip shield from the south, hopefully with no boundary layer or 850 trouble. Have not seen anything like that beyond an isolated model run, but it is still a week away.

 

Yes you remember a couple of East Tenn snow gems. Actually that was an inverted trough beyond just a moisture miscue. Apps may have a hand in the trough, adding a little cyclonic turn to the east wind aloft. Winds crossing mountain ranges and lee troughs (or inverted lee) are a whole other discussion. However I would not directly credit the Apps, as they can also create downslope (bad) with an ESE wind. It is the trough enhancing snow, a second derivative of the mountains, but not the mountains directly doing so that wind direction. Also even without mountains one can see inverted troughs, like in the flat Plains or Midwest. Basically it is an inverted extension of the main low, and, it can be a big help for snow. Models might miss the smaller scale feature, esp out a few days. Hi-res may pick it up better inside a couple days.

 

Regarding next post below: Yup ATL 2014 Snowmaggedon was an inverted trough, and it did the same thing to Chatty 1" but with such cold ground. Also last year 2015 when Chattanooga crushed the rest of the Valley we thanked an inverted trough. Note 2014 Huntsville-Chatty snow bomb was a vigorous coma head behind rain. I think the 2011 big snow was also helped by an inverted trough. 2015, 2014 and 2011 inverted troughs were cold and all snow baby!

[JayCee]

Two winters ago during a severe cold outbreak, there was a southern stream snow system that moved  to our south (the same one that made all the headlines in Northern Alabama and Atlanta, causing a traffic nightmare and shutting down their interstates).  I think this is the one mentioned above.  I remember a week out, models showed only snow flurries in East Tennessee.  I think 2 days before the system hit, the models starting latching on to an inverted trough situation that actually pulled some of the moisture back into East Tennessee.  I remember watching Todd Howell two nights before the storm, and he mentioned it in passing.  By the next night, the models were showing significant back building of the snow into East Tennessee.  We ended up with a little “snow gem” of a system—several inches of a powdery, Colorado type, snow that fell during the whole day.  It was particularly enjoyable for me, because I was home and the snow actually fell during the day (as opposed to overnight) when I could enjoy watching it fall, and since it was so cold, it started accumulating from the first flake—something unusual around these parts. J

[Carvers Gap]

Here is just a quick overview of some of the 0z suite...We will see if any new trends show-up on the 12z. 

 

GEFS ensembles compared to 0z yesterday are colder through day 16. 

 

The EPS through 360 depicts cooler than normal temps.

 

CMC has a threat near the end of its ten day run.  I don't know that any model can be trusted w/ the specifics outside of four days right now...if that.  It does have a general pattern of cold wx for the East w/ a pretty good shot of cold late in the run after a departing storm on the EC.  Again, the pattern is about all I am willing to comment on. 

 

Euro Deterministic is pretty suppressed w/ a stormy look around Jan 17th.  But that is a long way out there.  Maybe it is a signal for a storm and maybe not.  As we see w/ the Fri/Sat system...it is cutting to the Lakes.  But during the 16-17 time frame have to think suppression would be the biggest concern if indeed the threat is actually real.

 

GFS looked cold throughout. 

 

Overall, pretty tranquil pattern depicted on the 0z suite.  I strongly doubt it stays that way.  At one point the models had the time frame of the 10th-20th as pretty active.  So, just wonder if this is a case of models losing the pattern only to get it back within a few days of the event.  To be fair, the pattern is not exactly inactive w/ the strong storm headed to the Lakes this weekend.  With the MJO forecast to frolick in stage 8 and a record Nino...have to think more energy(across the South) is in the pattern than depicted.  Huge -NAO still shown on most models w/ ridging out west.  With a -NAO, -AO, and +PNA...I hate to use the word boring...but the pattern along the EC is pretty much forecast to be such.  I feel pretty strongly that until the big slp cuts to the Lakes and the strong -NAO matures...the models are going to struggle with the specifics of the pattern.  I like the pattern a lot.  Very blocky.  Sometimes you always ask yourself hypothetical questions regarding wx extremes.  Coming up one of those questions might get answered, "What exactly would happen if a record El Nino ran smack into strong blocking in North America?"  One would think that answer would be multiple winter storms in the East.  However, the jury is still out on that one... 

 

Closing fact.  KTRI is at -2.7 for January so far.  Not bad.  I noticed on my jog this AM that some areas in the creek were showing very early signs of being frozen.

 

Edit:  Also it is nice to see the quality posts from those who don't write as much on the board. 

[JayCee]

Thanks for the model overview CG. 

 

With the NAO/AO going deeply negative, perhaps it just a set up for late this month and into February.  Last winter was rather uneventful in January, but we more than made up for it in the final two weeks of February when the deep freeze engulfed us, along with multiple shots of ice and snow--one right after the other.  It was one of the few times, since moving here in 2003, that I had snow falling on top of two to three day old snow already on the ground.  Maximum coolness.

 

Also, the last two winters had multiple cold shots--some lasting a week or more.  But if memory serves, neither the AO/NAO went deeply into negative territory either winter.  At best, both would occasionally become slightly less than neutral.  I guess the big driver the last two winters really was the warm waters off of Northwestern North America.  At least that's one of the many theories I have heard.  In any event, it is extremely interesting to see how complex the Earth's climate really is.  SO MANY variables, indices and teleconnections to consider.   When I really ponder the complexity of it, I no longer wonder why man-made computer models do so poorly at forecasting, but instead, begin to marvel we could create any kind of computer program to forecast even a few days in advance, much less several weeks.