December 2022 Medium/Long Range Pattern Discussion Thread

[Carvers Gap]

12z EPS looks really good.  

[Carvers Gap]

The 0z EPS, 0z GEPS, 6zGFS operational(can't see the ensemble quite yet)....look fairly textbook w/ the block east of the MS.  Concern remains that the NAO could connect temporarily w/ the SE ridge, but if it does, I think that is very temporary.  Right now, I want to see if modeling can hit a double....-NAO followed by and EPO/PNA ridge.  

[Holston_River_Rambler]

And of course now that the MJO is getting into the western Pac all that nice convection from two weeks ago (that it might have helped enhance) has died out, lol

Although there is some south of Hawaii and east of Central America. 

 

[Holston_River_Rambler]

Also of note. I think we get an upgrade to the GFS today. 

[Carvers Gap]

The 6z GEFS moved back towards the EPS/GEPS solutions(getting the ridge out of the East in the LR).  I still think the we are looking at 10-14 days before the cold really begins to push southward.  If we can reel it in, some of us should have some chances at winter weather.  

[Carvers Gap]

32 minutes ago, Holston_River_Rambler said:

And of course now that the MJO is getting into the western Pac all that nice convection from two weeks ago (that it might have helped enhance) has died out, lol

Although there is some south of Hawaii and east of Central America. 

 

If we can steal some of January as cold, that is a victory.  Probably allows for a thaw mid-month...and then we wait and see if Nina weakens enough to allow winter to come back. It didn't come back in 10-11.  it didn't come back in 89-90.  But it did come back in 95-96. and maybe 09-10?

[tnweathernut]

The evolution of the blocking on the 6z GFS is one of the most extreme events I have seen at 500 since I started following modeling.  

[John1122]

The jostled PV and -NAO are signatures of the cold Southern Hemisphere in the upper levels that was discussed back in summer after the volcano put the water vapor up there and it caused the upper levels there to go extra frigid. 

 

[John1122]

5 hours ago, Holston_River_Rambler said:

Also of note. I think we get an upgrade to the GFS today. 

I'm surprised there's another one this quickly. Seems like it just upgraded last year. 

[Daniel Boone]

50 minutes ago, John1122 said:

The jostled PV and -NAO are signatures of the cold Southern Hemisphere in the upper levels that was discussed back in summer after the volcano put the water vapor up there and it caused the upper levels there to go extra frigid. 

 

Yeah, remember that being discussed; how it may affect blocking in the NHEM. 

[Daniel Boone]

6 hours ago, Carvers Gap said:

The 6z GEFS moved back towards the EPS/GEPS solutions(getting the ridge out of the East in the LR).  I still think the we are looking at 10-14 days before the cold really begins to push southward.  If we can reel it in, some of us should have some chances at winter weather.  

I think a bit sooner providing the NAO/ SER don't link. 

[Carvers Gap]

18 minutes ago, Daniel Boone said:

I think a bit sooner providing the NAO/ SER don't link. 

That is giving me great pause.  LOL.  I don't think they will but the GFS is trying to do this about half the time.  

[Carvers Gap]

Understandably, I don't think modeling(especially operationals) are handling the near record block which is forming.  

[Met1985]

Just now, Carvers Gap said:

Understandably, I don't think modeling(especially operationals) are handling the near record block which is forming.  

Yeah the operationals are going to be swinging a bit with this near record or record blocking in the NAO regions.  I wouldn't be surprised to see a storm pop up inside 5 to 7 days out of the blue given the extreme dynamics of this upper level weather pattern. 

[Carvers Gap]

1 minute ago, Met1985 said:

Yeah the operationals are going to be swinging a bit with this near record or record blocking in the NAO regions.  I wouldn't be surprised to see a storm pop up inside 5 to 7 days out of the blue given the extreme dynamics of this upper level weather pattern. 

For better or worse, I have been riding with ensembles of late.   I think you all are going to see some upslope at the very least.  

[Met1985]

1 minute ago, Carvers Gap said:

For better or worse, I have been riding with ensembles of late.   I think you all are going to see some upslope at the very least.  

That's definitely the way to go. Ensembles all the way. The OP models don't have a clue. 

[Carvers Gap]

12z EPS and seasonal CFS2(last run before December hits) is progressively cold with each passing week.  

[Daniel Boone]

3 hours ago, Carvers Gap said:

That is giving me great pause.  LOL.  I don't think they will but the GFS is trying to do this about half the time.  

Yeah, and we've witnessed that the last few years. That's something that almost never happened in the Winter back in the day. 

[EastTNWeatherAdmirer]

8 hours ago, John1122 said:

The jostled PV and -NAO are signatures of the cold Southern Hemisphere in the upper levels that was discussed back in summer after the volcano put the water vapor up there and it caused the upper levels there to go extra frigid. 

 

Hi, can you explain or elaborate more on why this is? Why does water vapor being pumped into the upper atmospheric cause cooling and what is the cause and effect relationship that exists in terms of the volcanic event promoting blocking on the other end of the pole(the northern hemisphere)? I’m not super keen on these kind of occurrences. Thanks in advance. 

[John1122]

2 hours ago, EastTNWeatherAdmirer said:

Hi, can you explain or elaborate more on why this is? Why does water vapor being pumped into the upper atmospheric cause cooling and what is the cause and effect relationship that exists in terms of the volcanic event promoting blocking on the other end of the pole(the northern hemisphere)? I’m not super keen on these kind of occurrences. Thanks in advance. 

Once water is injected into the stratosphere it reflects sunlight from above and keeps heat trapped below the stratosphere, which significantly cools the stratosphere itself. 

In this case, the cooling was record breaking. It occurred over the southern hemisphere and worked its way south toward the pole as their winter wore on towards spring. The colder the stratosphere over the poles the tighter the polar vortex tends to be. 

A study found that if the vortex is cold and tight over the south pole, it tended to be warmer and more jostled over the north pole. It also tended to feature a -NAO for decent periods in winter. 

As the vortex over the north pole gets jostled and the stratosphere there is warmed, it ejects cold air to the south. It doesn't always end up here but it goes somewhere into the northern hemisphere. However the -NAO pattern tends to lean colder here and more importantly, it tends to suppress the storm track towards a Miller A type track in winter. So having a PV that isn't locked tight and keeping cold air trapped well to the north should benefit our winter weather chances. 

[EastTNWeatherAdmirer]

The latest Canadian Climate Model’s Forecast for December: 

-really nice -NAO signature with undercutting jet

truly quite impressive to see so many models in unilateral agreement in regards to the prospect of a -Nao. Doesn’t mean we can count on it because the models haven’t been the best recently, but definitely a good signal for winter wx ❤️‘s!!!  

[EastTNWeatherAdmirer]

7 minutes ago, John1122 said:

Once water is injected into the stratosphere it reflects sunlight from above and keeps heat trapped below the stratosphere, which significantly cools the stratosphere itself. 

In this case, the cooling was record breaking. It occurred over the southern hemisphere and worked its way south toward the pole as their winter wore on towards spring. The colder the stratosphere over the poles the tighter the polar vortex tends to be. 

A study found that if the vortex is cold and tight over the south pole, it tended to be warmer and more jostled over the north pole. It also tended to feature a -NAO for decent periods in winter. 

As the vortex over the north pole gets jostled and the stratosphere there is warmed, it ejects cold air to the south. It doesn't always end up here but it goes somewhere into the northern hemisphere. However the -NAO pattern tends to lean colder here and more importantly, it tends to suppress the storm track towards a Miller A type track in winter. So having a PV that isn't locked tight and keeping cold air trapped well to the north should benefit our winter weather chances. 

Thank you. This is so helpful, interesting, and insightful. That’s cool you found a study stating that tendency/correlation. What study was it and who conducted it?

[John1122]

55 minutes ago, EastTNWeatherAdmirer said:

Thank you. This is so helpful, interesting, and insightful. That’s cool you found a study stating that tendency/correlation. What study was it and who conducted it?

https://www.severe-weather.eu/global-weather/cold-anomaly-stratosphere-polar-vortex-volcanic-cooling-winter-influence-fa/

[Carvers Gap]

Overnight ensembles continue to advertise a big switch between hour 240-260 which is just outside the 10day window.  I would expect to see more winter storms than I am seeing in fantasy land, but I also know that modeling has extreme difficulty handling the block.  The EPS is nearly perfect.  Remember that GFS run from many days ago that hooked the PNA ridge into the NAO block and trapped cold under it?  It had that, but the source region cold was not crazy cold - but probably cold enough.  That look normal delivers suppressed flow w/ some northwest flow components.

[Carvers Gap]

Here are the 5day(day 10-15)means for the 0z EPS....only fly in the ointment is BN precip.  Impressive for 5 day means.  Now, sometimes BN precip can actually reflect a snowy pattern.  Looks to me like the mid latitudes will feel the colder effects of the block around Dec 12th.  Modeling has bounced all over the place with trying to nail down the initial cold front, but ensembles generally favor that date.  With the initial cold being pushed back several days, the actual norms a colder as we are looking at mid-December vs early December.  This would be a pretty awesome score by modeling.  I feel like wx modeling will have nailed this from 3-4 weeks out(Weeklies).

 

[Carvers Gap]

What we see above is slider city which is one of the best ways we get snow for the entire forum area(E TN also gets snow from Miller A types, and middle/west score from Apps cutters and Miller B variations).  How suppressed will that storm track be?  IDK.  As noted by a met in the MA forum, modeling often will correct further south as the event gets closer which is opposite of "normal trending" which is north and west.  Where that boundary sets up is important.  I think we will see the boundary initially set-up over the Ohio Valley.  Whether that pushes further south will depend greatly on how much the SER fights back.  Oh yeah, the SER....it is present.   However, if one looks at the EPS d10-15, the block(and maybe double block) wipes it our for a TBD time frame.

[Carvers Gap]

And one last post within a flurry of posts, a bit of a SER is not a terrible thing w/ a block.  We want the STJ/southern branch to attack the block, and not just get suppressed to Cuba.  I suspect in coming days, we see that boundary get set quite far to the south.

[Carvers Gap]

I think we are going to see the -NAO hook into the SER for a 5-7 day time frame before mid-month.   That should open the door for very warm temps.  But it should be noted, that when the SER has connected into the NAO before, we have see the PV get hammered and split.  I think right now there are so many dynamics in play, it is just too many plates for models to handle.  That said, the potential for an NAO infused eastern ridge is growing.   If the EPS is right, that should retrograde westward fairly quickly.  The GFS/GEFS may have scored a coup on this feature.

[Daniel Boone]

1 hour ago, Carvers Gap said:

I think we are going to see the -NAO hook into the SER for a 5-7 day time frame before mid-month.   That should open the door for very warm temps.  But it should be noted, that when the SER has connected into the NAO before, we have see the PV get hammered and split.  I think right now there are so many dynamics in play, it is just too many plates for models to handle.  That said, the potential for an NAO infused eastern ridge is growing.   If the EPS is right, that should retrograde westward fairly quickly.  The GFS/GEFS may have scored a coup on this feature.

Yep, exactly what I feared. It's a shame we can't have -NAO setup while there's a -EPO and +PNA in place. 

[Carvers Gap]

9 minutes ago, Daniel Boone said:

Yep, exactly what I feared. It's a shame we can't have -NAO setup while there's a -EPO and +PNA in place. 

If the GFS(all runs today) is correct, the trough will set up shop in the West and just roll periodic cold fronts through the East.  I am definitely dialing back expectations now.