2025-2026 ENSO

[snowman19]

17 minutes ago, Stormchaserchuck1 said:

You don't do well in ++NAO/-PNA either

We may have to wait until the 2nd half of December for snowfall. 

If Paul Roundy is correct, the 2nd half of December is going to have more -PNA/RNA than the 1st half

[bluewave]

On 11/21/2025 at 11:43 AM, 40/70 Benchmark said:

This probably ties into the rule concerning the higher amplitude MJO waves in October preceding colder winters that @bluewavehas referenced, though I know that is a more recent phenomenon. I do wonder if those seasons were higher amplitude in October. Looks like 2010 would fit the mold...not so much 2005 and 2000. 

It’s good that all of us using different methods had a weaker PNA for this December than the record +PNA La Niña mismatch last December following the stronger amplitude MJO 5 over +2.70 in October 2024. 

[snowman19]

5 hours ago, 40/70 Benchmark said:

Yea, I said back to approaching climo by Xmas week, and that run reflects that.

Yes. You went against the grain and said weeks ago that you thought the November stratospheric warming was going to be a weaker wave reflection event and the SPV was going to rebound and strengthen quickly again mid-late December. If that works out, then it will have been a very impressive call

[MJO812]

1 hour ago, bluewave said:

The more +NAO following the wave reflection in concert with the stronger Maritime Continent forcing will both act to enhance the Southeast ridge as we had into December. Remember, the original forecasts for the first week of December didn’t have any Southeast ridge. Models regularly underestimate the Southeast ridge influence in the long range. Either through the 5 day means or with the storm track which amplifies the Southeast ridge on the days of the storms. 
 

New EPS December 1-8 forecast

Old EPS December 1-8 EPS forecast

 

 

The models are really struggling. Thanksgiving and its weekend warmup went poof so is the week 1 warmup which consists of plus 20 day skewing the entire week 

Here's another warm bust in the making 

 

[MJO812]

The 1st week of December does look mild though.  Delayed but not denied ?

Im going to remain patient. The Nina is dying and the MJO is going to go into 7/8 and most likely 1.

[EastonSN+]

2 hours ago, Stormchaserchuck1 said:

You don't do well in ++NAO/-PNA either

We may have to wait until the 2nd half of December for snowfall. 

Yeah unfortunately the RNA creates a SE ridge, and without blocking can facilitate cutters. 

This really feels like the old fashioned warm wet, cold dry years of the past. Last year we had plenty of cold but remained dry.

 

 

[EastonSN+]

2000 through 2018 was dominated by a positive PNA pattern which created troughing in the east the majority of the time. 

Unfortunately this has flipped to predominantly negative since 2018, hence more east coast ridge. We will get back to a positive PNA multi year pattern at some point. Just have to be patient.

[donsutherland1]

The CFSv2 has now moved into the early stages of its skillful range. Its monthly forecast for December is below. 

I assessed this idea against the currently expected state of the teleconnections. ENSO was omitted, as the sample size became so small that is was useless (n=2).

Based on the expected predominant state of the teleconnections for December (WPO-/EPO-/PNA- and AO neutral) it appears reasonable. The AO should start negative but could go positive as December progresses based on the current guidance. The second half outcome will depend on whether or not the stratospheric warming event propagates to the troposphere to  promote a redevelopment or persistence of AO blocking. So, for purposes of conservatism, I treated the AO as neutral (monthly average above -0.50 but below +0.50)  for looking at the monthly CFSv2 idea.

Should an AO+ regime develop (SSW fails to propagate in a fashion that promotes AO blocking), warm anomalies could cover much of the Eastern Seaboard with the exception of central or northern New England and have the risk of spreading into at least the Ohio Valley and perhaps farther westward depending on the strength of the AO+. For now, this is an identified risk, but not the most likely outcome.

On the other hand, should strong AO blocking develop, most of the eastern half of the U.S. would likely see cold anomalies. This scenario would also have the highest probability of seeing a strong Arctic outbreak reach the East Coast. Given the present guidance, this seems to be less likely than an earlier breakdown of the AO-. But the stratospheric warming event is a wildcard and how such events ultimately play out over long timeframes is not a high-skill undertaking.

It should also be noted that teleconnections cannot be forecast skillfully beyond 10-14 days. 

All in all, the combination of the CFSv2 and teleconnections highlights the Great Lakes Region and Upper Midwest as having the greatest probability of experiencing cold anomalies. They also highlight the Great Lakes Region as having the highest probability of above normal monthly snowfall. 

As for my thinking using the framework I illustrated yesterday, I've highlighted what has changed in my thinking overnight in blue. The emergence of a neutral AO on the guidance was noted (there's a very large spread among the ensemble members).

No changes were made beyond December 10 as signals remain mixed and there remains no clear signal for a change. 

[MJO812]

36 minutes ago, EastonSN+ said:

Yeah unfortunately the RNA creates a SE ridge, and without blocking can facilitate cutters. 

This really feels like the old fashioned warm wet, cold dry years of the past. Last year we had plenty of cold but remained dry.

 

 

All the ensembles bring down the cold after the first week.  No clue what the panic is right now.

[michsnowfreak]

44 minutes ago, MJO812 said:

All the ensembles bring down the cold after the first week.  No clue what the panic is right now.

People post from different regions so different effects are expected. Plus the select group of posters who always/only look for warm will be looking and scouring social media for whatever they need to to mitigate any cold. But overall appears that in typical nina fashion, the already cold north will have colder anomalies and the already warm south warmer ones. In other words big temp gradients, at least at times.

[stadiumwave]

https://x.com/judah47/status/1992608265507946858?t=ykLy8c-MkGuGLusD9eZevQ&s=19

 

[stadiumwave]

Paul Roundy's experiential MJO forecast tool has this look by DEC 14th...just updated.

 

https://www.atmos.albany.edu/facstaff/roundy/waves/rmmcyc/indexmjo.htmlGree

 

Very suppressed SER with big time -EPO & bridge block to Greenland. 

[Terpeast]

For future reference, based on MJO verification over the last 30 days, GEFS is really the one to watch when MJO is medium to high amplitude. And it’s not even competitive. 

[GaWx]

DJF MJO last 15 winters (2010-1 through 2024-5): # of days each phase

*7: 286 days from 58 phase 7s or 4.9 days/phase

*8: 95 days from 34 phase 8s or 2.8 days/phase

1: 76 days from 24 phase 1s or 3.2 days/phase

2: 96 days from 23 phase 2s or 4.2 days/phase

3: 167 days

4: 173 days

5: 212 days

6: 249 days

———————

  Per the above data, the # of phase 8 days for the last 15 winters, combined, has been only 1/3 the # of phase 7 days. This was due to a combo of much fewer phase 8 periods than phase 7 periods (34 vs 58) and much shorter avg. duration for 8 vs 7 (~3 days vs ~5 days). So, there sometimes is a struggle in going from phase 7 to 8. The # of combined 8-1-2 days has been ~# of phase 7 days, alone!

 The coldest E US phases have been 8, 1, and 2 while the warmest have been 4-6 (see bottom). The # of phase 8-1-2 days, combined, has only barely been higher than the # of phase 6 days, alone!

 So, as we look at Dec MJO progs, keep in mind the relative difficulty in getting as many phase 8 days (as well as each of phases 1 and 2, for that matter) as phase 7 days (if any at all). Just because models suggest a 2+ week long phase 7 is very likely doesn’t necessarily mean the durations of each of phases 8, 1, and 2 immediately following will be anywhere near as long, if they even occur.
 

 Here are the 10+ day long phase 7s since 2010-1 along with the subsequent phase 8-1-2:

- 1/14-30/13: 17 days followed by a combined 15 days in 8-1-2

- 2/19-29/2016: 11 days followed by a combined 10 days in 8-1-2

- 2/2-18/2018: 17 days followed by a combined 10 days in 8-1-2

- 2/7-21/2021: 15 days followed by 0 days in 8-1-2 and instead a combined 11 days in 6-5-6-7

- 12/19/2021-1/9/2022: 22 days followed by only 4 days in phase 8 before going back to 7; phases 7-6-5-4-3 then dominated the next 3.5 weeks.

- 1/1-10/2023: 10 days followed by a combined 9 days in 8-1-2

- 2/16-28/2023: 13 days followed by 1 day in phase 6 and then right back to phase 7 for 5 more days…so, 19 days in phase 7 for all practical purposes…followed by a combined 19 days in 8-1-2

- 1/28-2/6/2024: 10 days followed by 2 days in phase 6 and then right back to phase 7 for 10 more days….so, 22 days in phase 7 for all practical purposes…followed by only 1 day in phase 8, which was then followed by a combined 31 days in 7-5-6-7-3-4-5-6

———————

 Analysis of the above:

- Much more frequent 10+ day long phase 7 last 5 winters with 5 of them vs only 3 during the previous 10 winters!

- The combined 8-1-2 duration was never longer than the prior phase 7 length (using the “for all practical purposes” phase 7 length in two cases).

- Of the 8 long duration phase 7s, two (25%) of the following 8-1-2 periods lasted a notable length of 15-19 days and three (38%) lasted a mediocre 9-10 days. However, the other three (38%) were only a minuscule 4 or fewer days long (4, 1, 0) and these were all within the last 5 winters.

- So, whereas there’s a decent chance to get a higher end duration of 15-19+ days in 8-1-2 following the upcoming 7, the chance doesn’t appear to be very high and the chance of getting only a very disappointing short period is probably at least about as high.

- Thus, recent history tells us that the upcoming 2nd half of Dec MJO is practically un-forecastable as of now with dominance by the often cold 8-1-2 about equally as probable as a feared hardly any 8-1-2.
 

@donsutherland1@bluewave
———————

Daily MJO:

https://www.bom.gov.au/clim_data/IDCKGEM000/rmm.74toRealtime.txt

[MJO812]

This is clearly phase 8

[stadiumwave]

42 minutes ago, MJO812 said:

This is clearly phase 8

 

I am trying to figure out,is someone really saying it is not? And if so how can they say that? 

[MJO812]

2 minutes ago, stadiumwave said:

 

I am trying to figure out,is someone really saying it is not? And if so how can they say that? 

Look who keeps giving me weenies 

[Terpeast]

47 minutes ago, MJO812 said:

This is clearly phase 8

As I said, we will also want to see GEFS as comparison, not just the EPS

[Krs4Lfe]

One thing that I don't like is the lack of cold and snowstorms over CONUS thus far. I remember mentioning this in December 2023 and December 2024. Even years that were not good for us (2019,2020,2023) still had way more snowstorms and cold thus far. In many years, the snowstorms began as early as October, but even if it didn't begin in October, it began in November, and there would be a few large ones and several smaller ones as we neared December. Fall 2023, Fall 2024, and Fall 2025 have been virtually devoid of snow across CONUS outside of a few mountain ranges in New England and parts of the Great Lakes (and even then, that's been pretty muted). Part of this is likely due to the warmth in Canada, as that moderates temps across the northern tier, making most of their precipitation rain thus far. Ideally, you like to see a quick start to the season in October or November across the Plains and Upper Midwest, but like Fall 2023 and Fall 2024, that has been almost entirely absent this season. Snow begets snow, and cold begets cold. When that is absent from nearly the entirety of the US, with December right around the corner, that's never a good sign imo. I raised these points last November and December as well. 

[40/70 Benchmark]

5 hours ago, Stormchaserchuck1 said:

You don't do well in ++NAO/-PNA either

We may have to wait until the 2nd half of December for snowfall. 

I'll bet you $100 I have a plowable event of 3" or greater by the end of the second week of December (14th).

[MJO812]

1 minute ago, 40/70 Benchmark said:

I'll bet you $100 I have a plowable event of 3" or greater by the end of the second week of December (14th).

I think you will. 12z models are showing a better press with the storms ahead.

[so_whats_happening]

1 hour ago, MJO812 said:

This is clearly phase 8

Honestly I wish it could be as simple as saying we are going into a phase 8 pattern thus it should look like this. The issue going on is we are still in a Nina like background state but we are getting intrusions of Nino like features popping up. 

I honestly never thought this setup would work out as well as it is. Lets see how things continue

 

[40/70 Benchmark]

5 hours ago, bluewave said:

It’s good that all of us using different methods had a weaker PNA for this December than the record +PNA La Niña mismatch last December following the stronger amplitude MJO 5 over +2.70 in October 2024. 

I have a learned a ton from your material.

[bluewave]

2 hours ago, GaWx said:

DJF MJO last 15 winters (2010-1 through 2024-5): # of days each phase

*7: 286 days from 58 phase 7s or 4.9 days/phase

*8: 95 days from 34 phase 8s or 2.8 days/phase

1: 76 days from 24 phase 1s or 3.2 days/phase

2: 96 days from 23 phase 2s or 4.2 days/phase

3: 167 days

4: 173 days

5: 212 days

6: 249 days

———————

  Per the above data, the # of phase 8 days for the last 15 winters, combined, has been only 1/3 the # of phase 7 days. This was due to a combo of much fewer phase 8 periods than phase 7 periods (34 vs 58) and much shorter avg. duration for 8 vs 7 (~3 days vs ~5 days). So, there sometimes is a struggle in going from phase 7 to 8. The # of combined 8-1-2 days has been ~# of phase 7 days, alone!

 The coldest E US phases have been 8, 1, and 2 while the warmest have been 4-6 (see bottom). The # of phase 8-1-2 days, combined, has only barely been higher than the # of phase 6 days, alone!

 So, as we look at Dec MJO progs, keep in mind the relative difficulty in getting as many phase 8 days (as well as each of phases 1 and 2, for that matter) as phase 7 days (if any at all). Just because models suggest a 2+ week long phase 7 is very likely doesn’t necessarily mean the durations of each of phases 8, 1, and 2 immediately following will be anywhere near as long, if they even occur.
 

 Here are the 10+ day long phase 7s since 2010-1 along with the subsequent phase 8-1-2:

- 1/14-30/13: 17 days followed by a combined 15 days in 8-1-2

- 2/19-29/2016: 11 days followed by a combined 10 days in 8-1-2

- 2/2-18/2018: 17 days followed by a combined 10 days in 8-1-2

- 2/7-21/2021: 15 days followed by 0 days in 8-1-2 and instead a combined 11 days in 6-5-6-7

- 12/19/2021-1/9/2022: 22 days followed by only 4 days in phase 8 before going back to 7; phases 7-6-5-4-3 then dominated the next 3.5 weeks.

- 1/1-10/2023: 10 days followed by a combined 9 days in 8-1-2

- 2/16-28/2023: 13 days followed by 1 day in phase 6 and then right back to phase 7 for 5 more days…so, 19 days in phase 7 for all practical purposes…followed by a combined 19 days in 8-1-2

- 1/28-2/6/2024: 10 days followed by 2 days in phase 6 and then right back to phase 7 for 10 more days….so, 22 days in phase 7 for all practical purposes…followed by only 1 day in phase 8, which was then followed by a combined 31 days in 7-5-6-7-3-4-5-6

———————

 Analysis of the above:

- Much more frequent 10+ day long phase 7 last 5 winters with 5 of them vs only 3 during the previous 10 winters!

- The combined 8-1-2 duration was never longer than the prior phase 7 length (using the “for all practical purposes” phase 7 length in two cases).

- Of the 8 long duration phase 7s, two (25%) of the following 8-1-2 periods lasted a notable length of 15-19 days and three (38%) lasted a mediocre 9-10 days. However, the other three (38%) were only a minuscule 4 or fewer days long (4, 1, 0) and these were all within the last 5 winters.

- So, whereas there’s a decent chance to get a higher end duration of 15-19+ days in 8-1-2 following the upcoming 7, the chance doesn’t appear to be very high and the chance of getting only a very disappointing short period is probably at least about as high.

- Thus, recent history tells us that the upcoming 2nd half of Dec MJO is practically un-forecastable as of now with dominance by the often cold 8-1-2 about equally as probable as a feared hardly any 8-1-2.
 

@donsutherland1@bluewave
———————

Daily MJO:

https://www.bom.gov.au/clim_data/IDCKGEM000/rmm.74toRealtime.txt

Yeah, this is what I have been discussing. The rapid warming of the WPAC tropical SSTs near the near the Maritime Continent has been stalling the MJO in the warmer storm track and background temperature phases.

So the MJO progression tends to linger longer in the 4-7 phases and spend less time in phase 8.

This is why January 2022 was the last time that the RMM and VP anomaly charts were both solidly in Phase 8.

From March 2022 through the winter of 2024-2025 the few MJO 8s per the RMM charts had lingering forcing in phase 5-7 regions. So we didn’t fully realize the MJO 8 pattern which we last had in January 2022.

Many times the models try to rush the progression through phase 8 and it gets delayed and or weakened the closer in time we get to the forecast period.

This is what is shown when we subtract the last 16 years from the previous 16 years. You can see the stronger forcing closer to phases 6-7 where the warmest  SSTs on earth near +30C are found during the winter. This +28C +30C warm pool has been steadily expanding across that region.
 

 

[40/70 Benchmark]

4 hours ago, EastonSN+ said:

Yeah unfortunately the RNA creates a SE ridge, and without blocking can facilitate cutters. 

This really feels like the old fashioned warm wet, cold dry years of the past. Last year we had plenty of cold but remained dry.

 

 

Se Canada will be cold...they can cut all they want, it will have to snow at this latitude to advect the warmer air from the inland primary, and a triple point low will pop INVO cape cod as a byproduct of the initial resitance from the CAD.

[40/70 Benchmark]

16 minutes ago, bluewave said:

Yeah, this is what I have been discussing. The rapid warming of the WPAC tropical SSTs near the near the Maritime Continent has been stalling the MJO in the warmer storm track and background temperature phases.

So the MJO progression tends to linger longer in the 4-7 phases and spend less time in phase 8.

This is why January 2022 was the last time that the RMM and VP anomaly charts were both solidly in Phase 8.

From March 2022 through the winter of 2024-2025 the few MJO 8s per the RMM charts had lingering forcing in phase 5-7 regions. So we didn’t fully realize the MJO 8 pattern which we last had in January 2022.

Many times the models try to rush the progression through phase 8 and it gets delayed and or weakened the closer in time we get to the forecast period.

This is what is shown when we subtract the last 16 years from the previous 16 years. You can see the stronger forcing closer to phases 6-7 where the warmest  SSTs on earth near +30C are found during the winter. This +30C warm pool has been steadily expanding across that region.
 

 

Excellent post...mic drop-

[bluewave]

5 minutes ago, 40/70 Benchmark said:

Excellent post...mic drop-

Thank you for the kind words. It’s good to see that we can each use different methods and converge on similar solutions. You do a fantastic job putting together your seasonal outlooks. It’s why this extended format discussion forum is such a valuable resource bringing us all together in the same spot.

[mitchnick]

5 hours ago, donsutherland1 said:

The CFSv2 has now moved into the early stages of its skillful range. Its monthly forecast for December is below. 

I assessed this idea against the currently expected state of the teleconnections. ENSO was omitted, as the sample size became so small that is was useless (n=2).

Based on the expected predominant state of the teleconnections for December (WPO-/EPO-/PNA- and AO neutral) it appears reasonable. The AO should start negative but could go positive as December progresses based on the current guidance. The second half outcome will depend on whether or not the stratospheric warming event propagates to the troposphere to  promote a redevelopment or persistence of AO blocking. So, for purposes of conservatism, I treated the AO as neutral (monthly average above -0.50 but below +0.50)  for looking at the monthly CFSv2 idea.

Should an AO+ regime develop (SSW fails to propagate in a fashion that promotes AO blocking), warm anomalies could cover much of the Eastern Seaboard with the exception of central or northern New England and have the risk of spreading into at least the Ohio Valley and perhaps farther westward depending on the strength of the AO+. For now, this is an identified risk, but not the most likely outcome.

On the other hand, should strong AO blocking develop, most of the eastern half of the U.S. would likely see cold anomalies. This scenario would also have the highest probability of seeing a strong Arctic outbreak reach the East Coast. Given the present guidance, this seems to be less likely than an earlier breakdown of the AO-. But the stratospheric warming event is a wildcard and how such events ultimately play out over long timeframes is not a high-skill undertaking.

It should also be noted that teleconnections cannot be forecast skillfully beyond 10-14 days. 

All in all, the combination of the CFSv2 and teleconnections highlights the Great Lakes Region and Upper Midwest as having the greatest probability of experiencing cold anomalies. They also highlight the Great Lakes Region as having the highest probability of above normal monthly snowfall. 

As for my thinking using the framework I illustrated yesterday, I've highlighted what has changed in my thinking overnight in blue. The emergence of a neutral AO on the guidance was noted (there's a very large spread among the ensemble members).

No changes were made beyond December 10 as signals remain mixed and there remains no clear signal for a change. 

Cansips forecast for November has been very good. That's the seasonal I'm riding until it fails. 

[so_whats_happening]

Subsurface has been in a steady state for a bit now but we are starting to see a sharpening of the thermocline both warm and cold pockets so we may have some impact starting to show up in the 2 weeks from the MJO.

[Spartman]

8 hours ago, Stormchaserchuck1 said:

You don't do well in ++NAO/-PNA either

We may have to wait until the 2nd half of December for snowfall. 

December is looking like a write-off. Today's CFS v2 weeklies are a blowtorch all the way.