December 8-10 Storm Discussion

[Holston_River_Rambler]

"Fate often spares an undoomed man, if his courage is good." --Beowulf, Book VIII, lines 572-3.

 

Models seem set on a Gulf low with a banana High. The beginning of the storm over TX is in NAM range (stronger and further south with the High).Can we get the mid levels to wobble in just the right way? The WPC gives us all we could ask for at the surface at Day 4 in December, whatever ends up happening: 

 

EDIT to add in the end of the KMRX discussion this AM:

"At this range some of the details are unclear, but it does look as
if the potential for wintry precipitation Friday night and through
much of the weekend is possible/probable.  Details on ptype
timing/transition and precipitation totals will become more clear
over the upcoming days as this system is still over the Pacific and
not being observed in the RAOB network at this time."

[Holston_River_Rambler]

Top CIPS analogue for this one today is December 8-10, 1989. Here is a reanalysis animation of that one: https://imgur.com/a/GT2x39y 

It looks pretty similar, even to the secondary low developing as the energy at 500mb catches up, but not an exact match. 

How did we do? I don't remember, I was just 6 at the time. 

[Carvers Gap]

Here are the snowfall means for the 0z EPS and 6z GEFS.  

 

[Carvers Gap]

Interestingly, there are some almost Miller A/Noreaster solutions this AM.  The 0z CMC is a boomer w some energy transfer(not a fan of that...).  The FV3 makes an effort.  We need to watch that trend.  If that trend were to continue, that changes the entire equation if so.  I would not be surprised if it did.  

[tnweathernut]

49 minutes ago, Holston_River_Rambler said:

Top CIPS analogue for this one today is December 8-10, 1989. Here is a reanalysis animation of that one: https://imgur.com/a/GT2x39y 

It looks pretty similar, even to the secondary low developing as the energy at 500mb catches up, but not an exact match. 

How did we do? I don't remember, I was just 6 at the time. 

I think there was a cold shot and coastal snow in December of 1989, but it was later in the month...  if not mistaken.

 

[TellicoWx]

36 minutes ago, Carvers Gap said:

Interestingly, there are some almost Miller A/Noreaster solutions this AM.  The 0z CMC is a boomer w some energy transfer(not a fan of that...).  The FV3 makes an effort.  We need to watch that trend.  If that trend were to continue, that changes the entire equation if so.  I would not be surprised if it did.  

Yeah this thing is still in ensemble watch mode. Personally, an old friend of mine who was a met forever once told me 3+ days out =ensemble for upper pattern, 1-3 days = ops for the surface features, and under 1 day the meso models to fine tune things. The last 3 runs have seen the ensembles creep every slowly south and increase north of 40.

[TellicoWx]

Ensemble trends for last 9 GEFS and 4 EPS runs. Oldest>Latest Mean Snowfall

TRI: (GEFS) 3, 4, 4, 3.5, 3.5, 4, 4.5, 4.5, 6.5 (EPS) 1, 3, 5.5, 7

TYS: (GEFS) 2.5, 3.5, 3, 3.5, 3, 4, 3.5, 3, 5 (EPS) 3, 1.2, 2, 2.4

CROSS: (GEFS) 3.5, 5, 5, 4, 4.5, 5, 5, 3, 6 (EPS) 1, 3, 4, 4

The southern 1/4 of the state has generally stayed in the 1 to 1.5 range. While the OPs have been all over the place the last couple days, the ensembles have slowly been trending in the right direction for the upper half of the state.

[John1122]

The Euro seems to mostly be in line with it's ensembles, the GFS seems to want no part of it's ensembles. We will see who folds and which direction they fold in over the next 48 hours. Should get something closer to definitive by then. Crazy how hard is is to forecast for the entire Tennessee valley. Look how consistent the system is for the Carolina area. Even last year the models nailed big snows in crazy places in the deep South from pretty far out.  For our area it's just never easy or simple. I don't remember the last time a forecast came off without a hitch so to speak. 

[Carvers Gap]

I hope Holston does not mind...but I am going to post the MRX discussion that he posted along w the paragraph right before it.  Mainly, they are mentioning a Miller A(basically no energy transfer and the slp makes the turn).  I am very interested in the next two or three runs of modeling in terms of whether this becomes a full blown Noreaster'.  IMHO, that requires less finesse than this slider situation.  It will drag cold air into the system and likely pivot somewhere over the SE.  

Meanwhile, a fast moving shortwave will dive out of Canada into the
northern Plains while a cold Canadian high pressure airmass settles
behind the associated cold front.  This front looks to move across
the Midwest and into the OH valley by Thursday night, pushing
into the TN valley through Friday. Little if any precipitation is
expected with the fropa initially as moisture looks limited.
However, at the same time a southern stream H5 trough will
develop/deepen over the desert southwest, while surface
cyclogenesis is favored eastward over TX/LA. As this system tracks
east with the surface low oriented along the Gulf Coast in Miller
A fashion, moist upglide atop the established cold airmass
consequent of the old Canadian front will favor wintry
precipitation across portions of the southeast CONUS over the
weekend.

At this range some of the details are unclear, but it does look as
if the potential for wintry precipitation Friday night and through
much of the weekend is possible/probable.  Details on ptype
timing/transition and precipitation totals will become more clear
over the upcoming days as this system is still over the Pacific and
not being observed in the RAOB network at this time.

[Holston_River_Rambler]

On page 33 of the MA medium and long range there is a discussion of the Fv3 and some of its problems/ biases/ micorphysics.  It looks like someone who actually works on it for NOAA or NWS is explaining it.  Some of it also pertains to this storm. I'm not sure how much is a little banter between two Mets, so I won't repost here, and I'm not sure how to interpret everything they are saying, but if anyone wants to check it out, it's interesting. 

[Bango]

Lawdy at the crush in the nc mountains and piedmont from the 12z gfs, for under 5 days, might be the clown of all clowns for that region.

 

Still lightly snowing back in ky/tn some 48 or so hours later lol, although big totals are hit/miss above i40

[Carvers Gap]

The 12z suite so far (ICON, GFS, CMC) are starting to hone-in on a track and have some agreement.  It is notable to see the ICON put snow accumulations into the northern Valley on that run.  The CMC is a bit of an outlier w the energy transfer business, but somehow manages a similar snow axis.  NE TN does well on those runs w what would be a sharp cutoff to the west verbatim.  For E TN, the more this bends up the coast, the better.  It will allow things to pivot if we can keep the slp over the coastal plain and inside Hatteras.  Waiting on the FV3 at the moment...

[TellicoWx]

4 minutes ago, Carvers Gap said:

The 12z suite so far (ICON, GFS, CMC) are starting to hone-in on a track and have some agreement.  It is notable to see the ICON put snow accumulations into the norther Valley on that run.  The CMC is a bit of an outlier w the energy transfer business, but somehow manages a similar snow axis.  NE TN does well on those runs w what would be a sharp cutoff to the west verbatim.  For E TN, the more this bends up the coast, the better.  It will allow things to pivot if we can keep the slp over the coastal plain and inside Hatteras.  Waiting on the FV3 at the moment...

Yeah the 12z runs out so far are taking baby steps towards what you have been discussing this morning and what was in MRX write-up with a more traditional Miller A.

[jaxjagman]

17 minutes ago, *Flash* said:

12z GFS pumps up the backbuilding QPF. Would love this to verify, but I'm skeptical. Can't see the precip shield wrapping around like this based on how the 'L' is cutting. Boy do I wish this system would have phased up. Would have been a huge boost in forecast confidence.

 

Brings the ULL right over Tn,would be cool if it's right.We need all the help we can get here for snow in our parts

 

 

[TellicoWx]

Hearing the Ukie is coming in with a big, but little late phase now in the gulf.

[Carvers Gap]

1 minute ago, TellicoWx said:

Hearing the Ukie is coming in with a big, but little late phase now in the gulf.

Anyone have a link to those nice UK maps that were posted the other day w the satellite look?

[TellicoWx]

1 minute ago, Carvers Gap said:

Anyone have a link to those nice UK maps that were posted the other day w the satellite look?

Grit in SE forum said he was using the EWall 4 panel

[Holston_River_Rambler]

I saw Griteater post in the SE that the UKMET had a big phase, but slid the low south of Jacksonville, FL. All I can see are the panel types at 500 mb. Supposedly it's on an "ewall" http://mp1.met.psu.edu/~fxg1/ewall.html 

 

[Holston_River_Rambler]

Is this maybe it: http://mp1.met.psu.edu/~fxg1/UKHEMI_12z/ukloop.html 

No clue where the MA folks were getting the UK satellite maps from. 

[TellicoWx]

Very interested in what the GEFS and especially the UKie did, it is usually a precursor to the Euro.

[Carvers Gap]

I know if I was in charge of the FV3 maps during a big storm....I would be tempted to pause the output right before the most important map.

[AMZ8990]

35 minutes ago, *Flash* said:

12z CMC trolls west TN.  Double digit difference between Poplar Bluff and Dyersburg.

12z ICON also paints a reasonable picture with tempered amounts, but at least something to show for.

Overall, not only does the 12z suite capture Miller A/low track continuity, but also hints at cold air potentially catching up to make late Sunday/early Monday interesting. Could be off, but certainly looks like a favorable theme.

The Nashville snow dome moved west I see!! Haha

[Carvers Gap]

FV3 has finally moved....looks pretty similar to the rest of the 12z suite.   Bout all I have to say.  But I am pretty sure that I have all facets of the 96 hour map memorized.

[John1122]

I'm not even going to pretend to understand the FVS 3 at this point. It seems to show only rain here but piles up major snow. It's features were actually perhaps the best positioned for our region that I've seen so far. It's parent high was about 200 miles South of it's position last night when it dumped 2 feet on my area.

[John1122]

Looking closer at the FVS, it's pretty funny, the LP moves at two almost perfect 90 degree angles. The HP is further south initially so the low is actually further south of Panama City at 108 than it was last night. But instead of moving more smoothly NE like  basically any system would, it suddenly moves due North for 6 hours then moves due east for the next 6.  I guess that could technically happen, but it would be utterly bizarre for it to do so. I can't take that particular run of the FVS all that seriously due to that.

[TellicoWx]

12z GEFS mean:

[Bango]

What's up with the almost vertical jog north coming out of the gulf, centering in lower bama, on the fv3?  

[John1122]

4 minutes ago, Bango said:

What's up with the almost vertical jog north coming out of the gulf, centering in lower bama, on the fv3?  

No clue, I don't recall ever seeing anything like that actually happen before, but it's obviously technically possible. I'm personally going to discount it. I assume the model sees some brief weakness in the high over the top and thinks the system will slam the brakes on and shoot north but then be forced to resume eastward.

[Bango]

5 minutes ago, John1122 said:

No clue, I don't recall ever seeing anything like that actually happen before, but it's obviously technically possible. I'm personally going to discount it. I assume the model sees some brief weakness in the high over the top and thinks the system will slam the brakes on and shoot north but then be forced to resume eastward.

Without that hiccup, and smoothing out the trajectory starting south of panama, I am guessing it would look like the ever so southerly version of its 6z path. Dunno how that would affect the northern areas of tenn?

[nrgjeff]

Northwest Tennessee, Kentucky, Tri Cities Tenn, and southwest Virginia have a decent chance of snow. Nashville, Clarksvile and Knoxville need a miracle. I'd take MEM-HSV-CHA off the table.

Middle Kentucky has the trickiest path with the warm nose. West Kentucky and northwest Tennessee benefit on the northwest side. East Kentucky is at a higher elevation. Tri Cities into Virginia are closer to the coldest air from the north, but the warm nose will make a run up the Valley.

High pressure HP is strong but lacks very cold air. Unfortunately for points south, HP is strongest east of the Apps. Needed strongest HP west of Apps. Also 500/700 mb lows are at/north of US-72 which takes it out of snow consideration.

Areas that receive snow will likely start as rain. TROWAL feature on some models may help snow on back side (north/favored only). TROWAL is basically a good comma head. Precip is enhanced by WAA from the warm nose into colder core on the back side. TROWAL would only benefit north/favored side of Region. TROWAL post coming in Education thread..

Northern third of our Region still has many challenges; however, it remains in the game for snow. I'm thinking northwest Tenn, Kentucky, TRI, Virginia.