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Wintry Winter 25-26 Winter Battle Zone

I just looked up -ENSO winters with a -PNA in Dec to see how often it went to a +PNA in Jan. In what winters did this occur?

-1954-5: -0.52 to +0.40

-1962-3: -0.08 to +0.58

-1983-4: -0.31 to +0.97

-1984-5: -1.60 to +1.63

-1996-7: -1.23 to +0.63

-1998-9: -0.09 to +0.16

-2008-9: -1.41 to +0.61

-2010-11: -1.78 to +1.29

-2012-3: -1.01 to +0.55

-2013-4: -0.86 to +0.97

-2016-7: -0.35 to +0.28

-2021-2: -2.56 to +1.01

-2022-3: -0.66 to +0.22

So, although it wasn’t common from 1954-5 through 1971-2, when only 2 of 9 (22%) switched, here’s something that just blew my mind:

-ALL 11 -ENSO -PNA Decs since 1983-4 switched to +PNA Jans (listed above)!

-These 11 averaged +0.76 in January!

-Now, check out the -ENSO Jan PNAs since 1983-4 that had a +PNA in Dec:

1) 1985-6 went from +1.39 to +0.97

2) 1988-9 went from +0.63 to -0.72

3) 1995-6 went from +0.92 to -0.02

4) 1999-00 went from +0.21 to -0.82

5) 2000-01 went from +1.23 to +1.51

6) 2001-2 went from +0.56 to -0.04

7) 2005-6 went from +1.38 to -0.43

8) 2007-8 went from +0.14 to -0.32

9) 2011-2 went from +0.36 to +0.60

10) 2017-8 went from +0.89 to +0.40

11) 2020-1 went from +1.58 to +0.19

12) 2024-5 went from +1.70 to +1.05

-So, for these 12 -ENSO Decs since 1983-4 with a +PNA, only 50% also had a +PNA in Jan.

-So, since 1983-4, whereas only 50% of the 12 -ENSO Decs with a +PNA also had a Jan +PNA, 100% of the 11 -ENSO Decs with a -PNA in Dec went to a +PNA in Jan! Thus, having a -PNA in Dec during -ENSO since 1983-4 has, if anything, meant a big increase in the chance for a +PNA in Jan whether random or not! I didn’t know this til just now.


Link to monthly PNA table:
 
GaWx said:
I just looked up -ENSO winters with a -PNA in Dec to see how often it went to a +PNA in Jan. In what winters did this occur?

-1954-5: -0.52 to +0.40

-1962-3: -0.08 to +0.58

-1983-4: -0.31 to +0.97

-1984-5: -1.60 to +1.63

-1996-7: -1.23 to +0.63

-1998-9: -0.09 to +0.16

-2008-9: -1.41 to +0.61

-2010-11: -1.78 to +1.29

-2012-3: -1.01 to +0.55

-2013-4: -0.86 to +0.97

-2016-7: -0.35 to +0.28

-2021-2: -2.56 to +1.01

-2022-3: -0.66 to +0.22

So, although it wasn’t common from 1954-5 through 1971-2, when only 2 of 9 (22%) switched, here’s something that just blew my mind:

-ALL 11 -ENSO -PNA Decs since 1983-4 switched to +PNA Jans (listed above)!

-These 11 averaged +0.76 in January!

-Now, check out the -ENSO Jan PNAs since 1983-4 that had a +PNA in Dec:

1) 1985-6 went from +1.39 to +0.97

2) 1988-9 went from +0.63 to -0.72

3) 1995-6 went from +0.92 to -0.02

4) 1999-00 went from +0.21 to -0.82

5) 2000-01 went from +1.23 to +1.51

6) 2001-2 went from +0.56 to -0.04

7) 2005-6 went from +1.38 to -0.43

8) 2007-8 went from +0.14 to -0.32

9) 2011-2 went from +0.36 to +0.60

10) 2017-8 went from +0.89 to +0.40

11) 2020-1 went from +1.58 to +0.19

12) 2024-5 went from +1.70 to +1.05

-So, for these 12 -ENSO Decs since 1983-4 with a +PNA, only 50% also had a +PNA in Jan.

-So, since 1983-4, whereas only 50% of the 12 -ENSO Decs with a +PNA also had a Jan +PNA, 100% of the 11 -ENSO Decs with a -PNA in Dec went to a +PNA in Jan! Thus, having a -PNA in Dec during -ENSO since 1983-4 has, if anything, meant a big increase in the chance for a +PNA in Jan whether random or not! I didn’t know this til just now.


Link to monthly PNA table:
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Larry, If the rmm charts are accurate, the ensembles and models should reflect sooner rather than later.
 
SimeonNC said:
It feels like we've already kicked the can from early December to now mid-December lol
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Not really. Even I've said & agreed that later in December looked better for winter storm potential.

Btw, I'm still expecting us to transition from a -PNA/-NAO to +PNA/-NAO type pattern here in early December. That probably will happen once the -EPO block retrogrades back into Siberia & accelerates the exit region of the Pacific Jet. My guess is that happens probably near the end of the first week into the 2nd week of December.
Webberweather53 said:
Still suspect we will see a transition from a -PNA/-NAO late Nov to +PNA/-NAO/-EPO in early December as the upper-level footprint of the MJO goes from the West Pac (phase 7) to the Western Hemisphere (phase 8). This CPC outlook in week 3-4 is the average of these two patterns.

Very tricky sensible weather forecast in the Carolinas and Mid-Atlantic tho with potential for some wild swings. We may find ourselves in the battle zone between cold CAD nosing in from New England and substantial bouts of milder air trying to push in from the Southern Plains & Lower MS Valley

We should see the -NAO/-EPO persist for the bulk of December and progressively lose the +PNA late in the month as the MJO re-enters the Indian Ocean again late December or so (phase 2). Of course, there’s absolutely nothing wrong with that, especially if we’ve got a respectable amount of snow cover and cold already entrenched over the CONUS. Losing the +PNA may just mean many more opportunities for storms with much better late Dec climatology to boot as @1300m alluded to
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We've talked about the upcoming -EPO episode nearly a month ago, things are mostly going as I thought they would so far. That includes the MJO progression into the Western Hemisphere.

Webberweather53 said:
Latest Euro weeklies generally make sense to me.

Big +EAMT driven jet extension this week drives a trough over the Gulf of Alaska and it slowly retrogrades as November progresses w/ -EPO appearing late in the month into early December as this trough reaches the Kamchatka Peninsula. We could be cooking right off the hop this winter over the CONUS

View attachment 175639
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Stevo24 said:
It was never early December. However someone mark this post. Cause if we start talking about the end of December here in a week or two I think we have begun can kicking.
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Webberweather53 said:
Not really. Even I've said & agreed that later in December looked better for winter storm potential.

Btw, I'm still expecting us to transition from a -PNA/-NAO to +PNA/-NAO type pattern here in early December. That probably will happen once the -EPO block retrogrades back into Siberia & accelerates the exit region of the Pacific Jet. My guess is that happens probably near the end of the first week into the 2nd week of December.



We've talked about the upcoming -EPO episode nearly a month ago, things are mostly going as I thought they would so far. That includes the MJO progression into the Western Hemisphere.
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Eric, sometimes pattern changes get delayed more than we first thought due to unforseen situations. It's what makes weather fascinating
 
MRKEVIN7575 said:
Eric, sometimes pattern changes get delayed more than we first thought due to unforseen situations. It's what makes weather fascinating
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The -EPO is here late Nov as expected, the Canadian warming event is occurring as you expect it would following a pacific mjo event during a Nina winter, and we'll probably see a transition out of this -PNA/-NAO in late Nov before the -PNA probably tries to come back again with the next MJO orbit into the eastern hemisphere near the end of December. Don't see the issue
 
Jack Frost said:
The poster 1300m won't be returning. The forum isn't looking for a professional meteorologist who can accurately forecast (speaking of cowards, who was too scared to enter the snowfall contest and take me on like a man last winter?), that's why they keep you around, to provide inaccurate long range hopium. Keep up the good work from all the way out in NM 🤣.
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Im hopeful we will get at least one opportunity at a winter event in my area, which we only average 4-5 inches snow a winter. Maybe some sleet and fzr also. It's probably a little less in the southeast
 
Today’s 12z GEFS probably isn’t too far off in the grand scheme of things if this blocking ridge over the Bering Sea is generally in the right place by this point in time.

The details (timing and placement etc) will move some, but should see a big, healthy chunk of the troposphere polar vortex drop to near the Hudson Bay at some point.


IMG_6616.png

IMG_6609.jpeg
 
Followup: here’s the average temp. anomaly of all Decs, Jans, and Febs for -ENSO winters since 1983-4 with a -PNA in Dec:

Dec (all had -PNA with avg. -0.99): slightly warmer than normal E US (most pronounced SE) and very cold N Plains/Rockies:
IMG_5444.png


Jan (all had +PNA with avg. +0.76): slightly colder than Dec Chicago S and E but N Plains/Rockies not as cold:
IMG_5446.png


Feb (all 11 PNAs dropped back down with Feb avg. PNA of -0.19): other than GA to TX, this is easily the warmest of 3 months averaged out in the E 2/3 of US with warmest SC to NE:
IMG_5447.png
 
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Idk if this post belongs here but I just wanna bring this up for those who view last Monday's cold snap as a waste.

If we had a trough like that even in December let alone January, it probably would've resulted in a classic dry cold pattern that very few of us actually like. I've noticed over the years that arctic outbreaks don't usually produce winter storms for us

Also, I personally don't view cold weather and good patterns as a limited resource that can be wasted lol
 
Fool's Gold. The LR euro weeklies are not to be trusted.
ecmwf-weeklies-avg-nhemi-z500_anom_7day-1763164800-1765152000-1765152000-20.gif

Webberweather53 said:
Euro weeklies, extended GEFS, and CMC weeklies all pretty much have the general same idea wrt the NAO and PNA as we head into early December

View attachment 176093


View attachment 176094

View attachment 176095

The low frequency base state + MJO + Eq Rossby Wave analog also agrees
View attachment 176096
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1300m said:
My confidence is still low for early December. IMO, unless you are looking for heartache, I wouldn't be putting any stock in the long range ensembles / weeklies. Last 14 run loop for week 1 of December shows how clueless the euro weeklies are.

View attachment 176098View attachment 176099

MJO forecasts continue to slow down in P7 now well into the first week of December. That is not going to help with getting a favorable eastern U.S. pattern going.

View attachment 176100View attachment 176102

Allan also makes a good point about the lag between an SSWE and resultant impacts - another reason to doubt December is going to come in with a winter pattern already established for us. If the MJO lags in P7 through week 1 of December + SSWE doesn't occur until around early December, we're looking at realistically week 2 or week 3 before an atmospheric response to those impulses would be expected and that is if they even occur at all.



I see a lot of competing factors for early December as it stands now, which leads me to believe early December may not feature a locked-in winter weather regime with a strong west-based -NAO and a downstream eastern U.S. trough and favorable Pacific, but as always, would love to be wrong.

If confidence in the MJO moving into P8 increases, I'll feel a lot better about things, but I remain skeptical of that happening as of now considering the research done showing the present -NAO we have may actually increase potential for the MJO to not move in that direction, but instead work against it.
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Some people have to learn the hard way about these and that’s fine.
 
MRKEVIN7575 said:
When do you believe a more favorable pattern for cold and wintry weather east of the rockies may evolve? Just curious
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Week 2 - 3 of December. It will take time for the full atmospheric response to the weakened SPV + eventual P8 MJO to occur. First true southern winter storm threat could be the week of Christmas if things go right!
 
Jack Frost said:
Week 2 - 3 of December. It will take time for the full atmospheric response to the weakened SPV + eventual P8 MJO to occur. First true southern winter storm threat could be the week of Christmas if things go right!
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I live in west tennessee and like i mentioned before, we average 4-5 inches snow a year, but I like our opportunity when we get them!
 
Jack Frost said:
Fool's Gold. The LR euro weeklies are not to be trusted.
View attachment 176712




Some people have to learn the hard way about these and that’s fine.
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The EPO/NAO/AO and general idea of a west pac to western hemisphere mjo orbit were all there even that far out. The PNA will probably follow suit once the North Pacific block runs its course.
 
GaWx said:
Followup: here’s the average temp. anomaly of all Decs, Jans, and Febs for -ENSO winters since 1983-4 with a -PNA in Dec:

Dec (all had -PNA with avg. -0.99): slightly warmer than normal E US (most pronounced SE) and very cold N Plains/Rockies:
View attachment 176709


Jan (all had +PNA with avg. +0.76): slightly colder than Dec Chicago S and E but N Plains/Rockies not as cold:
View attachment 176710


Feb (all 11 PNAs dropped back down with Feb avg. PNA of -0.19): other than GA to TX, this is easily the warmest of 3 months averaged out in the E 2/3 of US with warmest SC to NE:
View attachment 176711
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For 1983-4+ -ENSO: Now I’ll compare the 3 winter maps when there’s been a -PNA in Dec (see those in what I’m quoting) to the same for a +PNA in Dec:

+PNA Decs: significantly colder than -PNA Decs (as expected) and coldest of DJF from Mack’s abode E and S
IMG_5448.png


Jans following +PNA Decs: warmer than Jans that followed -PNA Dec (almost entire US) and warmer than those +PNA Decs, themselves, Plains eastward; warmest of DJF Plains eastward except SE/MidAtlantic
IMG_5449.png


Feb following +PNA Decs: mild E 1/4 of US but coldest of DJF Plains to Pac NW
IMG_5450.png
 
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Today’s Euro Weeklies shows the likelihood of a reversal has shifted to now favoring ~11/28 over 11/25:

Today’s Euro Weeklies favors 11/28-9:
IMG_5452.png

The runs from 3 days ago and earlier favored an 11/25 reversal:
IMG_5406.png

Add in the typical several week lag and a potential of a mid-Dec phase 8 MJO followed hopefully by phases 1-2 and we’d have a realistic chance for a several week long period of cold domination in the E US starting as early as mid-Dec. Prior to this potential, there’d also likely be a mild dominated next 30 days, which shouldn’t be ignored.
 
Webberweather53 said:
Yeah that looks about right.

Pretty much copy & paste the last 30 years worth of La Niña Decembers.

View attachment 176720

View attachment 176721
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GaWx said:
Today’s Euro Weeklies shows the likelihood of a reversal has shifted to now favoring ~11/28 over 11/25:

Today’s Euro Weeklies favors 11/28-9:
View attachment 176722

The runs from 3 days ago and earlier favored an 11/25 reversal:
View attachment 176723

Add in the typical several week lag and a potential of a mid-Dec phase 8 MJO followed hopefully by phases 1-2 and we’d have a realistic chance for a several week long period of cold domination in the E US starting as early as mid-Dec. Prior to this potential, there’d also likely be a mild dominated next 30 days, which shouldn’t be ignored.
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CFS is very tame for the EAST and South thru Dec 18th. Some cold air but no sign of snow.
 
Can’t help but notice, the weeklies progression is like many -EPO events, but especially February 2014. Notice, starts out with a -PNA given the developing/maturing stage of the block, then the block starts to cutoff/retrograde, this allows the jet to accelerate further and chop of the block further, allows eastward progression of the cold (we get one peice, the other piece gets shoved back towards AK, then as the block regrades further, the troughing around AK does as well, and it forms a canonical +PNA. This same feature also could encourage another strong -NAO episode to show up, and by then, we would have a legitimate Arctic source in NH
1
IMG_9892.jpegIMG_9898.png
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IMG_9893.jpegIMG_9899.png
3
IMG_9894.jpegIMG_9900.png
 
Myfrotho704_ said:
Can’t help but notice, the weeklies progression is like many -EPO events, but especially February 2014. Notice, starts out with a -PNA given the developing/maturing stage of the block, then the block starts to cutoff/retrograde, this allows the jet to accelerate further and chop of the block further, allows eastward progression of the cold (we get one peice, the other piece gets shoved back towards AK, then as the block regrades further, the troughing around AK does as well, and it forms a canonical +PNA. This same feature also could encourage another strong -NAO episode to show up, and by then, we would have a legitimate Arctic source in NH
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View attachment 176724View attachment 176727
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View attachment 176725View attachment 176730
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Yeah this step down process is how these type of pattern changes typically evolve. Never made sense to think early December was going to go gangbusters right out of the gate. As long as we can keep the MJO on schedule, I feel great about weeks 3 & 4 of December. Great analysis.
 
As a weather newbie, I've been lurking and learning for many months. Excited to join and for the prospects of the forthcoming winter. As a former Floridian/now North Alabama transplant, winters are a LOT more interesting up here.
 
Myfrotho704_ said:
Can’t help but notice, the weeklies progression is like many -EPO events, but especially February 2014. Notice, starts out with a -PNA given the developing/maturing stage of the block, then the block starts to cutoff/retrograde, this allows the jet to accelerate further and chop of the block further, allows eastward progression of the cold (we get one peice, the other piece gets shoved back towards AK, then as the block regrades further, the troughing around AK does as well, and it forms a canonical +PNA. This same feature also could encourage another strong -NAO episode to show up, and by then, we would have a legitimate Arctic source in NH
1
View attachment 176724View attachment 176727
2
View attachment 176725View attachment 176730
3
View attachment 176726View attachment 176729
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Yeah as we talked about in one of our chats earlier this week, that’s normally how these big North Pacific blocking events evolve in winter.

About 2 weeks after the peak of the -EPO is usually when the core of the cold swings eastward as northerly flow on the backside of the retrograding block over Siberia raises the EPO enough to accelerate the pacific jet and dislodge the cold from the Rockies.

 
256wx said:
As a weather newbie, I've been lurking and learning for many months. Excited to join and for the prospects of the forthcoming winter. As a former Floridian/now North Alabama transplant, winters are a LOT more interesting up here.
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Welcome aboard to the most entertaining weather forum in sports entertainment!
 
256wx said:
As a weather newbie, I've been lurking and learning for many months. Excited to join and for the prospects of the forthcoming winter. As a former Floridian/now North Alabama transplant, winters are a LOT more interesting up here.
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Can you handle the pain and suffering? If so, welcome aboard!
 
Stevo24 said:
Can you handle the pain and suffering? If so, welcome aboard!
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Haha! I have pretty low expectations. One event of the white stuff a year is enough to keep me happy. So far, I am 3 for 3 in years I have been here. Although it was a bit wild watching my former home in Pensacola get dumped on this past winter! We still had a 4 inch event at my house, so I was happy for them.
 
256wx said:
Haha! I have pretty low expectations. One event of the white stuff a year is enough to keep me happy. So far, I am 3 for 3 in years I have been here. Although it was a bit wild watching my former home in Pensacola get dumped on this past winter! We still had a 4 inch event at my house, so I was happy for them.
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Alabama has faired well recently. My area not so much. Last good one was 22. We are due. But honestly we are all due for a big one.
 
Webberweather53 said:
If we get a near or below average December with even a trace of snow this year, I'd consider that a win given how the last decade has largely gone.

View attachment 176731
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Makes you wonder how that was possible to pull off? Wasn't like 7 of those years La Nina? Clearly La Nina isnt acting like La Nina in Dec. Of course February though its doing exactly what its supposed to do
 
RainlessSnowless & Grumpy said:
Makes you wonder how that was possible to pull off? Wasn't like 7 of those years La Nina? Clearly La Nina isnt acting like La Nina in Dec. Of course February though its doing exactly what its supposed to do
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Yeah we had a heavy dose of Nina in there and those few big Nino Decembers (esp 2015) were roasters which didn’t help.

Honestly, this year feels like a throwback, more in line with how Decembers used to look in the 2000s.
 
Webberweather53 said:
If we get a near or below average December with even a trace of snow this year, I'd consider that a win given how the last decade has largely gone.

View attachment 176731
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Jack Frost said:
Pretty incredible how warm the past decade of Decembers have been in NC. Definitely overdue for a cold one.

View attachment 176733
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Helping make this warmth possible has been the lack of phase 8 MJO during the last 10 Decembers. Actually, there’s been only one Dec phase 8 of 3 days+ since 2009 and that was during 12/21-24/2017! That’s crazy! Compare that to the 7 of the prior 15 years and the 10 for the 15 years before that! (Ironically though, 12/21-24/2017 was mild in RDU/E US though we know they’re not all cold but rather ~80% BN to MBN in RDU.) Some of this was bad timing with them being either in late Nov or early Jan. But a good bit of it was the MJO detouring around 8.

That’s why I’m not at all assuming a multi-day phase 8 will definitely occur. Taking it with a grain for now.
 
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