December 2018 Pattern And Forecast Discussion

[nrgjeff]

First I enjoy reading the Obs thread for the past weekend storm. Thanks for letting us who were blanked live vicariously, lol!

This weekend (Dec 15 ish) looks elevation only. Models blank the Plateau, but Upper Plateau snow is possible back side. Models have snow in the Mountains based on both the ULL and upslope behind. 

System looks like a loser at lower elevations. It is stacked and getting barotropic. Prefer baroclinic with a deepening surface low, which is not shown. This will be my last post about Dec 15 if nothing changes.

Meanwhile it looks like a colder pattern will try to rebuild starting around Christmas; however, surface effects may be after Christmas. Could be a cold New Year. For now the warm period looks a little longer than I'd thought, 10-14 days vs 5-7 days. Does not seem like a deal killer for more cold later. MJO is just in a warm phase, which will pass. Models have more signs of Alaska ridging and other blocking by Christmas. Again it might take until the New Year reflect on the surface in the Southeast.

While I may sound pretty meh about upcoming storms, I am still optimistic about January. Cold pattern on top of cold climo is friendly if one likes snow.

[Carvers Gap]

Not much to add...Jeff's comments pretty much sum up the next couple of weeks.  What is a very good sign is that we have had two storm tracking threads already for this winter, including one in November.  These El Nino winters are often "go big or go home" type systems.  One notable thing about this last storm is that the bullseye for the GEFS/EPS was money from some time out.  The edges of the bullseye are where amounts varied.   It is very rare to track a system from 7-8 days and have the bullseye verify.  This storm is a testament to how far modeling and data ingest has come.  

This wet snow is melting fairly quickly.  I am still somewhat concerned that we get a rainmaker at elevation and potential flooding on mountain streams.   Just need to keep an eye out for any significant rainy systems at elevation.  

For KTRI, they will begin the winter w about 10" in early December of what should be a good snow year.  If we have normal to AN snow for January and February, the season total could be pretty high.  I always consider snow before Christmas to be "bonus snow."  

[dwagner88]

The miss this weekend worries me a bit for the southern portion of our forum area. From a climo perspective, the areas of NC that cashed in big time are very unlikely to have another snowfall of a similar size this year. This worries me because systems that create decent snows in the southern valley almost always create even better snows in those same areas of NC. Basically, if we were to get hammered in this area later in the winter, a lot of NC would break seasonal records downstream from us. This seems quite improbable. I hope we didn’t just waste our best shot. 

[nrgjeff]

Chattanooga thoughts first; then, the Weeklies. Previous storm (12/8-9) does not worry me too much. Sure Chattanooga and Asheville are often on the same storm track, but not always. This time the cold air was only on the NC side of the Apps. I remember I think 2015 CHA got several inches while NC lower elevations got a dry slot. Occasionally we diverge. Depends on the set-up. True though CHA/AVL are often on the same storm track, just not always. Wichita-KC-Chicago is another example of often, but not always. 

Ensembles and Weeklies are somewhat consistent. Warm period, with variability, is still in the cards later this week until Christmas, give or take. Warmth is supported by MJO blossoming convection approaching warm zones (for the SE). Remaining cold zone convection is diminishing. Early next week could be a couple seasonably cold days. Infer another CF weekend of the 22nd. No storm systems of note, except that elevation deal this weekend. CF around 21-22 Dec way too early to tell. Overall looks mild until Christmas.

Western US should start getting cold week of December 24. Except for those brief fronts mentioned above, I think the pattern changing cold will start out West. SER could be in place early Dec 24 week. First attempted cold front would probably fail. Reinforcements could eventually undercut the ridge. Euro weeklies gradually get colder Southeast in January but it's weeks 5-6. Those weeks have pushed back cold one week; and, clusters show more scatter now. That is normal behavior, but not as bullish as a couple runs prior. 

January will become more clear as the MJO wave mentioned paragraph 2 works itself out. Hopefully. Probably variable cold, vs sustained perfect pattern.

[Carvers Gap]

Much appreciation to Jeff for the Weeklies update.  Yeah, not a surprising run.  It fits Nino climatology like a glove.  Many warmups in December are often followed by a backloaded winter.  It is a fairly consistent script.  The stratosphere getting bumped around may make LR forecasting touch and go.  I can remember Nino winters with long periods of cool, rainy weather followed by a 2-4 weeks of intense winter weather during the second half of January and/or February.  

[Carvers Gap]

BTW, I am not writing off the first half of January by mentioning the "second half" of January.  Just was referring to climatology.  Jeff has a great timeline in his post.  

[BlunderStorm]

So temperature wise where do we stand across the forum and how do you all think we will stand by the end of the month?

[Carvers Gap]

I have to admit, I wasn't expecting the 12z GEPS and the GEFS to looks that good in the LR...but the look pretty good.  The EPS is now within the winter season and should be more consistent.  It is not on board...but it does not have the support of the GEPS/GEFS right now.   All three show a warm-up.  All three show it end.  The GEPS/GEFS combo is the one w an earlier chance at a return to winter.

[Daniel Boone]

Regardless of how the weeklies look, with the extended warm period, the way this season has gone thus far, it is possible it will be wrong as it was a couple weeks ago when many(including mets) bought into it. Yes, the Mjo is discouraging but, other factors have been known to mitigate it's effects. Definitely not saying the long mild period won't happen, just looking at the possible bright side. 

[Holston_River_Rambler]

3 hours ago, BlunderStorm said:

So temperature wise where do we stand across the forum and how do you all think we will stand by the end of the month?

I bet -0.5 overall by the end of the month. It's 11 days in and only a couple have been warmish/ average so far. Maybe average to slightly above this week and then the storm this weekend should keep us a bit below, then a week of average to ever so slightly below. Then it's only one week left in the month and even if that week isn't terribly cold it could be a little cooler and if there are storms, even if they are rainy, that still = cooler than average.

Looks like for Knoxville average today is around 51 and that average only drops to 47 by the end of the month. I don't see a ton of days above the low to mid 50s coming up. 

As of today:

Knoxville = -0.3

Chattanooga = -0.5

Tri-Cities = +0.4

Oak Ridge = +0.3

Nashville = -0.8

Clarksville = -1.1

Crossville = -3.2

Memphis = -4.4

Jackson = -4.2

Huntsville = -1.4

 

 

 

 

[Carvers Gap]

Time to look forward after a week of big snow for some and earthquakes for others...and the week isn't even over!  Anyway, just looking at the LR, I am encouraged by the 12z GEFS/EPS looks.  They are not new to the party either.  They have yet to buy-in to the EPS look.  The FV3 looks pretty good as well in the LR - reference @Queencitywx in the SE forum  I know the EPS is not a great look.  However, there are come contradictory looks as we get to Christmas and beyond.  It is entirely possible that the GEFS is getting the pattern right but is too quick on the evolution of the pattern.  It is also entirely possible that the EPS is dragging its heals again in the SW just like it did last winter.  And again, anytime we speculate about the d10-15, it is just that - speculation.  Take it with a huge grain....

And we haven't even dug too deeply into the potential strat warm yet...maybe more on that later.

[Carvers Gap]

So maybe we can kick around the strat warming possibility.  JB mentioned that if this happens, the following 60 days are general BN w the colder temps showing up about 30-40 days after the event.  He also noted that there is not need to hurry this set-up as we want February to be cold - I am sure that probably helps his forecast as well.  Here is a tweet from Ventrice.  I really like the information that he and Amy Butler(stat guru) put out there.  This "potential" event will likely make LR models a mess after Christmas.  The strat warming event could lay the groundwork for a cold January and February.  Posting tweets helps me save on attachment space and I can credit the poster at the same time.

 

[Carvers Gap]

So what does all of that mean?  Looks like a stratospheric event could be in the works just before Christmas.  It might take a couple of weeks to work its way down to our region.  However, the impact on the stratosphere will be quick.  Might take a couple of weeks for blocking to really take hold and deliver cold air into Eurasia and/or North America.  Ideally, we would see a split that sends cold into both continents.  

[nrgjeff]

Who in this sub-forum Region? (I do not check other regions often.)

23 hours ago, Daniel Boone said:

Regardless of how the weeklies look, with the extended warm period, the way this season has gone thus far, it is possible it will be wrong as it was a couple weeks ago when many(including mets) bought into it. Yes, the Mjo is discouraging but, other factors have been known to mitigate it's effects. Definitely not saying the long mild period won't happen, just looking at the possible bright side. 

Going theme here from myself, Carvers, and others, has been please don't panic. Warmth won't last forever. In fact personally I had too few warm days.

I am not looking for a big debate or he-said she-said. However, I would like the flow of information and recollection of the discussion to be accurate. Benefits new members and lurkers. Thanks!

[Daniel Boone]

3 hours ago, nrgjeff said:

Who in this sub-forum Region? (I do not check other regions often.)

Going theme here from myself, Carvers, and others, has been please don't panic. Warmth won't last forever. In fact personally I had too few warm days.

I am not looking for a big debate or he-said she-said. However, I would like the flow of information and recollection of the discussion to be accurate. Benefits new members and lurkers. Thanks!

First off Brother, there was no pun thrown toward anyone in the subforum.. I have always respected and looked forward to your input as well as others. I apologize for any misunderstanding. What I posted was accurate and meant as I stated, to be on a positive note. Carvers had made mention recently of how the weeklies did that last month and yes, there were Mets and others that bought into it. Btw, I'm not just a novice poster or weenie for that matter. Been around as long or longer than many on here. Health went down a few years ago along with a life altering event of which I retired from meteorology.  Since, I want to remain anonymous. Carvers may have an idea of who I am. I enjoy being back in the discussions as weather has been a passion of mine for over 40 years. I must say, my reception and respect on here from what it was during my previous time is about like night and day. 

[Vol4Life]

Daniel, I’ve enjoyed your posts.  Please keep posting!

[Holston_River_Rambler]

I respect and value everyone who posts in this region. I honestly can't think of anybody here who doesn't meaningfully contribute. (Some other regions it can get a little wild and wooly). Looks to me like there's just been a misunderstanding.

This form of social media is the only one I really care about because we all try and care. 

[Daniel Boone]

31 minutes ago, Vol4Life said:

Daniel, I’ve enjoyed your posts.  Please keep posting!

Thanks Vol . Much appreciated! Btw, I'm a Vol fan as well.

[AMZ8990]

On 12/11/2018 at 3:45 PM, Holston_River_Rambler said:

I bet -0.5 overall by the end of the month. It's 11 days in and only a couple have been warmish/ average so far. Maybe average to slightly above this week and then the storm this weekend should keep us a bit below, then a week of average to ever so slightly below. Then it's only one week left in the month and even if that week isn't terribly cold it could be a little cooler and if there are storms, even if they are rainy, that still = cooler than average.

Looks like for Knoxville average today is around 51 and that average only drops to 47 by the end of the month. I don't see a ton of days above the low to mid 50s coming up. 

As of today:

Knoxville = -0.3

Chattanooga = -0.5

Tri-Cities = +0.4

Oak Ridge = +0.3

Nashville = -0.8

Clarksville = -1.1

Crossville = -3.2

Memphis = -4.4

Jackson = -4.2

Huntsville = -1.4

 

 

 

 

I knew it had been chilly on my side of the state so far this month.  I didn’t realize we were at -4 though.  That’s pretty impressive given our past few December’s out this way. 

[Carvers Gap]

The 0z GEFS looked to be heading into the Euro camp for d10-15.   The 6z left that camp, and doubled down on nationwide cold.  The GEPS continues w a nationwide cool down from Christmas onward.  The GEFS mean does hint at a winter storm signal from d10-15.  I am sure you all see the same things I see on the operational modeling in regards to that.  The 0z EPS moved quite a bit overnight by placing a bit more trough in the east.  It is almost(not quite) a reversal w its 850 d10-15 temps.  At 12z yesterday there were warm 850s over the SE.  This morning they are reversed w cold in the nation's mid-section and cooler air over the forum area.  Again, I look at 5 day means for trends in this regard.  The change is noticeable.  In some ways, it looks like modeling wants to go w a full latitude NA trough w the cold dropping west and spreading east.  Honestly, it feels like deja vu.  Last winter, the models were cold in the very LR, flipped warm, and then gradually returned to their original solution by late December.  Then, it turned very cold.  Anyway, understandably a very fluid situation at that range...and again, this is pure speculation and not a forecast.  

[Holston_River_Rambler]

42 minutes ago, AMZ8990 said:

I didn’t realize we were at -4 though

When I saw that on the NWS climate data, I thought I was reading it incorrectly. Didn't think there could be that much diff. across the state. As far as I can tell though, that was it.  

Also want to quickly ay that I was not trying to put words in anyone's mouth with my thought last night, just trying to say I saw what looked like a misunderstanding, so apologies if it came off as though I was trying to say anything else. 

No big changes as far as can tell this AM (EDIT for the above: mostly talking about cold returning overall and the strat. Carver's has got the 500 mb and temp trends covered). 

Stratosphere still looks like some sort of warming is coming, but actual effects at midlevels and surface/ how the warming itself evolves still up in the air. I would say that even if it happens (looks likely to me, though again how it plays out and eventual results are murky at best).

One interesting feature that the GFS is struggling with is some cut off 500 mb energy over TX/ N Mexico/ Gulf in the day 8-10 time frame.  GFS really wants it to just set there and spin for a bit. Today's 6z run it links it up with some N stream energy coming in hot and pops an east coast storm. This is just one run of one model at 8 -10 days so very, very unlikely at this point.  But I am interested to see how this evolves.  Having some energy sit over the Gulf or N. Mexico could get interesting in a variety of ways if the timing is good, but no point in talking details on anything like this I'd say until much closer.  Sure it could get tapped into as part of a bigger storm, but it could also just scoot out to the Atlantic.  Sometimes we use football analogies and I think a good one for this situation is the "if you want to beat a big team, keep it close into the 4th quarter". The longer that energy sits there, the more chances it has to cause mischief. It's there on the Fv3, maybe 5-6 6zGFS ensemble members have it, and I'd say maybe 30-40% of Euro ensemble members have it too, but everything deals with it in different ways at different times, as you'd expect with a cutoff at 8-10 days just close enough to the overall flow to be impacted by it. 

 

 

[nrgjeff]

Looks like the end of December is coming into a little better focus now. I'm thinking it might actually get seasonably cold Christmas week. Probably it will not be all week though. Could be another few warm days between Christmas and New Years.

A look at the tropical Pacific and Indian ocean shows a cluster of convection around Indonesia a warm signal valid coming right up. Some of it is diurnal though (weaker warm signal), right over the Islands, so a CF ahead of Christmas is reasonable. Meanwhile a bigger blob of convection lurks in the Indian Ocean. Should it emerge into the Pacific, viola the warm days between the Holidays.

Then the bigger return to cold pattern should commence in January. CFS wants another warm week, but nah. ECMWF weekly due out tonight has been cold. Both agree around Jan 7-10 get some robust cold going. That is week 5-6, but at least they agree. Look for the MJO to shift toward colder signal phases.

@Daniel Boone I was pretty sure you were talking about outside this subforum Region. I appreciate all of your posts! Certainly agree respect goes both ways. I give students/hobbyists the same professional treatment as Mets because it's the right thing to do. Everybody here has important knowledge from local effects to technical discussion. Flip side is I press, which is actually a sign of professional respect, because I know everyone here can provide reasoning.

At any rate we got a good thing going in this subforum Region. I do not plan to post about the Euro weeklies unless they change significantly. Figure January cold will start West and work in here. Timing could still be by the New Year.

[Carvers Gap]

The QBO is officially positive at +3.36.

[Daniel Boone]

Thanks Jeff, its all good man. Great analysis ! In hopes, with the right timing we can score a Christmas surprise. 

[Carvers Gap]

Jeff's analysis above definitely covers the range of outcomes from now until the cold potentially returns during the second week of January.  The 12z EPS is definitely back in the camp of a warm-up between New Year's and Christmas.  It does look like it is retrograding a trough from the West Coast to a position in the Pacific(SE of AK) where it could pump a -EPO in early January.

[PowellVolz]

Thanks Jeff, its all good man. Great analysis ! In hopes, with the right timing we can score a Christmas surprise. 

Yeah you do a great job and Tennessee fan here also.


.

[Carvers Gap]

I am assuming that the quiet pattern discussion thread means that we all see what is cooking in the long range.   Looks like a cool shot around Christmas followed by roughly a couple of weeks of warm temps if the Weeklies are even remotely correct.  A quick look at the day-by-day means on the Weeklies show a trough in the West establishing itself after Christmas.  Sometime around January 7th, that pattern breaks down at 500 and BN heights develop slowly over the SE.  It takes maybe another 7-10 days for 2 meter temps to respond.  By the third and fourth weeks of January we are in business.  This is why Nino winters drive me crazy.  The are often backloaded for the second half of winter.  Even when I know this is going to happen, it tests my patience.  That said, we have stolen a couple of storms from the pattern already.  The progression is a classic, classic Nino progression.  Now, I don't like seeing the cold pushed back...but it makes sense.  (I also don't like what the JAMSTEC just outputted.)  As soon as I saw the big blue blob over AK, I knew the tough out West was going to be a pain.  

Now, the pattern is still highly active.  It can and does snow during warm-ups during El Nino winters.  We had marginal cold for this last storm and still managed a whopper in NE TN.  So, really all I can urge right now is patience as we begin what will likely be a warm 3-4 week time frame which will have some cold embedded.  I am just hoping that my warm-up prediction mojo reverts back to its November form.  Ha!

Now, for an ounce of hope...the American operational suite is not totally buying the prolonged warm-up and is blocky.  Per JB, how the Euro suite and American suite is handling the MJO might be different.  It may be possible that the Euro is stalling the MJO in phase 4.  If so, hence the warmth(Jeff mentioned that yesterday I thing) after Christmas.  I just have a difficult time seeing the trough tanked in the West knowing what we know about Nino winters.  One caveat, the SOI is (from what I understand) still hanging around in Nina territory. Also, the QBO just recently flipped positive....

Anyway...the skinny is warmth after Christmas for 2-3 weeks with a backloaded winter still likely.  My thinking has not changed a bit on that....

[Carvers Gap]

Regarding d10-15....That was a significantly warm run of the 12z EPS.  The EPS within four runs has shifted d10-15 500 mean from a weak trough over the East to a very stout ridge.  The control has some daily +23C 850 temps AN over Michigan. +15C here late in that time period.  The mean for 850s is about +5-7C AN.  We can only hope this busts as badly as it did in November.   The actual mean 2m temps are roughly +4-7C late in the period(not a 5 day mean...).   The control has some daily 2m temps that are nearly +20C over the eastern Plains and western Ohio River Valley late in that time period.  Not as bad here, but you get the picture.  I give it much less credence after that month.  The GEFS is not nearly as bullish nor is the GEPS.  That is a pretty big swing by the EPS within four runs of the 5-day mean.  It is also out there where it is less than accurate, but still...the Euro suite has gotten very consistent with this look. 

One final note on the Weeklies.  The NAO mean was modeled to go negative around the New Year.   At the same time the -AO will couple with that teleconnection around the same time frame.  The +PNA goes weekly positive shortly after.  If you had just shown me the teleconnections, I would have guessed that the model output would have been much colder.  Maybe it is a source region problem after the Canadian torch passes through just prior.  Not sure.  So, it is unusual to see the model respond so slowly to those teleconnections in terms of cold.

I expected some warmth during an El Nino winter, but maybe not to that level....Hopefully this is muted as what is modeled on the EPS is well past anything that I had envisioned. Hoping the American suite takes the W on this one.  As for the Euro, this gif pretty much is for it.......

[Carvers Gap]

Now, we are about to test a theory from last spring.  I think there is some science behind it.  I just can't remember where I read it, and am too lazy on Friday afternoon to Google it.  Remember when the WAR went crazy, and then the strat split happened.  I wonder if exceptional warmth over NA(especially the eastern half), precedes it?  

[Holston_River_Rambler]

I feel like everything is in a wait and see mode, like the parts in a rube-goldberg machine are being built and about to be set off. There's so much going on that seems to be setting up more and once it all starts, where shall it go? 

We have a Nino that is a little west based, a little east based for now: 

We have a stratospheric polar vortex that is getting manhandled and redirected like a Cobra Kai kid trying to fight off Mr. Miyagi.

We have an MJO that is weakish (going by CPC latest discussion http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/mjoupdate.pdf, pages 16-17), but hopefully lining up to come back to the more favorable phases by early Jan. 

 

I think it will be interesting to see how all this plays out once it happens and how the models deal with it as it begins to impact their starting conditions.

 

I feel like Gandalf and Pippin in Return of the King: 

Pippin: "It's so quiet."

Gandalf: "It's the deep breath before the plunge."