December 2022 Medium/Long Range Pattern Discussion Thread

[TellicoWx]

28 minutes ago, Daniel Boone said:

Really need that TPV to assert under the block to help stave off that thing from cutting. That's the piece of the Puzzle that's missing and hurting the portrait from being a masterpiece.

     Strong LP under that block, whether 50-50 , 60-40, or even 70-30 for that matter should get it done.

    The Blizzard in the Dakota's is an example of a Storm cutting and going toward the block before stalling. A strong enough system will cut without a strong enough mechanism to weaken or shunt it. 

I remember tracking one several years ago that had a similar solution at this range (except the roles were reversed between GFS/Euro). Everyone (myself included) thought the GFS was out to lunch...storm ended up cutting straight into the block. So agree with you completely.

[Carvers Gap]

1 hour ago, Matthew70 said:

Sad to see after this cold blast it warms up for a chilly rain.  44-50.  TWC says Jan. thaw all month.

They are probably riding the 89-90 analog.  The 500mb map is good for most of Jan(through the 20th at least).  The source region is suspect as Canada is scoured by cold.  But...we only need seasonal temps to score in January.  I tend to lean 10-11 as my analog for this year.  There is a pretty decent signal for cold during the second and third weeks of January.  

[Carvers Gap]

It is important to remember....we still have ~ten more weeks of winter. 

[Carvers Gap]

I am going to use the other thread for the 23rd system for right now.  The 6z GFS is trying to get something going on the 25th now as well.

[Carvers Gap]

It appears the 6z GFS has another round of light snow in western forum areas on Christmas completely unrelated to the storm on the 23rd/24th.  Yep, looks like a northern stream piece of energy is diving in along the Arctic boundary.  If real, that is a good look as cold air is already in place - a slider.

[Carvers Gap]

The Canadian has this but is a day later.  That would be a very good look for people also in southern areas of the forum.

[Carvers Gap]

My main take away from last night's runs is that the pattern may very well be active even after the cold front comes along.  The boundary gets set, and systems slide along it.  Northern stream emphasis is a nickel and dime ticket, but it does pay.  The CMC and GFS both have this look.  The Euro is sort of on an island after d7....edit the CFSv2 does support is somewhat just not to that extreme.

[Carvers Gap]

Will be out and about today, so hold the fort down.  The LR on the CFSv2 does have the Chinook.  The good thing is it looks like a +PNA type of pattern for January.  If so, that will work.  We just need normal temps to score in January.

[tnweathernut]

4 hours ago, Carvers Gap said:

Will be out and about today, so hold the fort down.  The LR on the CFSv2 does have the Chinook.  The good thing is it looks like a +PNA type of pattern for January.  If so, that will work.  We just need normal temps to score in January.

Overall, I’m encouraged by what we are seeing in December.  Popping a PNA and watching a beautiful block form leads me to believe we will have our chances this year………….aside from whatever we can try to find (snow wise) from the 22-27th.  
 

It’s early on and I guess I’m just happy to not be staring at 70s for Christmas.  Although I do admit as I get older, warmer weather bothers me less and less.  lol

[Matthew70]

1 hour ago, tnweathernut said:

Overall, I’m encouraged by what we are seeing in December.  Popping a PNA and watching a beautiful block form leads me to believe we will have our chances this year………….aside from whatever we can try to find (snow wise) from the 22-27th.  
 

It’s early on and I guess I’m just happy to not be staring at 70s for Christmas.  Although I do admit as I get older, warmer weather bothers me less and less.  lol

Same here. Older I get the less tolerance for cold I have. If it turns out dry & this kinda cold.  My patience will be tested. I will definitely be saying come on spring .  

[EastTNWeatherAdmirer]

Is it just me or does it seem like the -NAO has done more harm that good this year so far? I may be 18 years old but I’m old enough to remember the claim so many people say that a -NAO is good for the Mid-Atlantic and Eastern Seaboard. It seems like the NAO, or at least the variation of it this year, has been detrimental for us in the South and East. The massive low 500 miles ESE of Nova Scotia caused by the negative NAO has caused buckling in the jet further back west, over us, with only mediocre heights and a subtle upper ridge nudging and grudging it’s way over us again and again. Sure, Europe has definitely seen the cold and snow and it might just be the unfavorable Pacific; but, for us here in the East this massive -NAO has done nothing but churn higher 500 mb heights up into it along the Eastern Seaboard and that looks to be the case with the 22/23 system with basically a repeat of Dec 15 in the East, just colder this time. You might think I’m a clown(emoji here) but what the **** is wrong with this -NAO?

[jaxjagman]

MJO is showing some decent signs as we head into Jan,we should warm up tho  before this.The Euro and GFS are on the same page with heights rising in East Asia and a ULL over Mongolia,this seemingly will rise the heights in the east and probably promote a -PNA,possible severe stroms somewhere,GFS also is showing this.But FWIW i already see signs of the Greenland /AK block try to establish itself once again as the MJO seemingly works back into the WH and Africa,we shall see i guess.

[Carvers Gap]

4 hours ago, EastTNWeatherAdmirer said:

Is it just me or does it seem like the -NAO has done more harm that good this year so far? I may be 18 years old but I’m old enough to remember the claim so many people say that a -NAO is good for the Mid-Atlantic and Eastern Seaboard. It seems like the NAO, or at least the variation of it this year, has been detrimental for us in the South and East. The massive low 500 miles ESE of Nova Scotia caused by the negative NAO has caused buckling in the jet further back west, over us, with only mediocre heights and a subtle upper ridge nudging and grudging it’s way over us again and again. Sure, Europe has definitely seen the cold and snow and it might just be the unfavorable Pacific; but, for us here in the East this massive -NAO has done nothing but churn higher 500 mb heights up into it along the Eastern Seaboard and that looks to be the case with the 22/23 system with basically a repeat of Dec 15 in the East, just colder this time. You might think I’m a clown(emoji here) but what the **** is wrong with this -NAO?

I placed an answer in banter.  Look no further than the upcoming cold shot than to see its effects.  An active subtropical jet (STJ) would have had us digging out for a month.  Nina climatology (dry) is fighting us all the way.  Many historic Kocin storms and historic cold outbreaks have -NAOs.  The bigger issue is the lack of frequency in regards to precip.  That is related to issues on the Pacific side and not Atlantic.  Additionally, one teleconnection is rarely the magic bullet.  The PNA/EPO is a great pattern for middle and west TN.  Sometimes it is just the luck of the draw.  Without the NAO, we are probably sitting in the 70s for December w/ the rising QBO and poor Pacific set-up (to this point).  The NAO is actually offsetting some really bad teleconnections.  When the NAO relaxes(if we don't have a strong enough PNA), watch what happens w/ temps....

[Carvers Gap]

4 hours ago, EastTNWeatherAdmirer said:

Is it just me or does it seem like the -NAO has done more harm that good this year so far? I may be 18 years old but I’m old enough to remember the claim so many people say that a -NAO is good for the Mid-Atlantic and Eastern Seaboard. It seems like the NAO, or at least the variation of it this year, has been detrimental for us in the South and East. The massive low 500 miles ESE of Nova Scotia caused by the negative NAO has caused buckling in the jet further back west, over us, with only mediocre heights and a subtle upper ridge nudging and grudging it’s way over us again and again. Sure, Europe has definitely seen the cold and snow and it might just be the unfavorable Pacific; but, for us here in the East this massive -NAO has done nothing but churn higher 500 mb heights up into it along the Eastern Seaboard and that looks to be the case with the 22/23 system with basically a repeat of Dec 15 in the East, just colder this time. You might think I’m a clown(emoji here) but what the **** is wrong with this -NAO?

Additionally, December is rarely our month for snow.  It has been recently, but historically the valley rarely scores big snows prior to the fourth week in December.  Our best climatology is January to the first week of February.  So, we are fighting general climatology as well.  NAOs are often the coldest in January and February.  In general, it doesn't want to snow in the valleys during December - even old school eras as well.  

[Carvers Gap]

One thing I always have to remind myself.  We live at a latitude known as the subtropics.  It wants to rain here for all but six weeks out of the year(Jan-early Feb).  

[Carvers Gap]

One last note about the -NAO...a strong NAO in December is closely correlated to it returning mid and/or late winter.  The CFSv2 shows a zonal pattern to end the month, and potential cold reload quickly thereafter.

[Silas Lang]

 

13 minutes ago, Carvers Gap said:

Additionally, December is rarely our month for snow.  It has been recently, but historically the valley rarely scores big snows prior to the fourth week in December.  Our best climatology is January to the first week of February.  So, we are fighting general climatology as well.  NAOs are often the coldest in January and February.  In general, it doesn't want to snow in the valleys during December - even old school eras as well.  

If I am remembering correctly, I think March is even typically better than December for snow. 

[Coach B]

1 hour ago, Silas Lang said:

 

If I am remembering correctly, I think March is even typically better than December for snow. 

Pretty sure you are correct. I know Nashville averages more snow in March than December. Obviously March is warmer, but its also prone to some big hitters with snow. December, seems to be more likely to have little nickel and dime events.

[Tullioz]

On 12/16/2022 at 3:59 PM, Carvers Gap said:

The one I am thinking of is a line graph w/ time as the x-axis and model verification as the y-axis.  One model is represented w/ triangle points, another squares, and so on.....I am heading out the door or would dig a bit more.

If you haven't found it already, I think this might be what you're looking for:

https://www.emc.ncep.noaa.gov/users/verification/global/gfs/ops/grid2grid_all_models/acc/

[Carvers Gap]

10 minutes ago, Tullioz said:

If you haven't found it already, I think this might be what you're looking for:

https://www.emc.ncep.noaa.gov/users/verification/global/gfs/ops/grid2grid_all_models/acc/

Perfect.  The GFS is scoring decently at d7.  It was terrible a few weeks ago, has now cleaned up its act.

[Carvers Gap]

The CMC is showing ice on the 22nd for the eastern valley.  I don't see that on other modeling, but something to watch.  That set-up is one way to get it.  When rain approaches from the SE, there is air pushed down the west slopes of the Apps(warming those slopes due to compressed air...downsloping), the cold gets pushed in the deepest parts of the TN valley and west slopes of the Plateau....and ZR.  I don't think it is overly likely as the thermal profile on the CMC is colder.  Time of day is important.

[Carvers Gap]

 

[Carvers Gap]

LR Update:  Looks like we see a warm-up from Dec28-10th.  The EPS led the way w/ this by sniffing out the Pacific flooding the continent w/ maritime air.  We "may" still have a trough in the SE, but that is not for certain, and source regions are certainly suspect on modeling.  Is this a pattern change or just a temporary relaxation?  TBD.  We need to see if the can keeps getting kicked down the road as far as a return to cold.  I "think" cold returns fairly quickly, but I could certainly see a scenario where cold returning taking a lot of patience.  Normal temps get the job done here in January.  Lots of fluidity in the pattern to start January.  

[Silas Lang]

1 hour ago, Carvers Gap said:

 

That would be awful with the cold temps following. I do think we might have to be concerned with flash freezing if the cold comes in as quickly as modeled. 

[Carvers Gap]

2 minutes ago, Silas Lang said:

That would be awful with the cold temps following. I do think we might have to be concerned with flash freezing if the cold comes in as quickly as modeled. 

It likely would melt before the second system arrives.  This is the front runner system.  Again, I can't find it on any other modeling.  

[Holston_River_Rambler]

Ensembles starting to get the floody look way out there. Jet accelerates over the TN or OH Valley as the mean trough dumps in the center of the US and we land on the right entrance region:

EPS:

 

GEFS:

 

Could change on a dime, but we know how we do with rain in a La Nina, so......hopefully it passes through or some blocking modulates it south of us. 

[Carvers Gap]

Digging through the LR ensembles and CFSv2.  I am not so sure whatever warm-up we have is going to be very short lived.  I originally though Jan10th as the time to return to cold.  Just looking at things, the PNA is going to fire almost immediately as the current pattern breaks down.  The EPS backs the trough to the middle of the country and then sends it eastward as the run ends.  The CFSv2 at 12z is quite similar..  The EPS run-to-run change d10-15 is quite cooler.  Again, like a broken record, normal temps will get the job done in January.  

 

As for flooding, many a cold pattern has been preceded by excessive rain....

[Carvers Gap]

And one point further, the GFS operational is quite different from the CMC/Euro operationals.  As we have seen w/ the system later this week, the GFS got smoked.  We certainly should warm-up, and that warm-up has been fairly evident as a ridge rolls through.  It looks like "for now" that ridge keeps on going and the trough settles right back.  The GEPS barely warms up at all, and it has led the way in terms of cold severity in d10-15.  Big message -> lots of variability after d5....lots.  

[Carvers Gap]

Food for thought.

[Carvers Gap]

The 12z CMC rolls a ridge through on the 28th-29th(EPS is a hair slower and ensuing trough more centered in Kansas prob a bias in play there).  The pattern reloads at HL almost immediately after that.  Then, the PNA fires.