2025-2026 ENSO

[WVclimo]

1 hour ago, MJO812 said:

Euro is now colder in the long range . All the models have trended colder. 

Euro is frigid

[40/70 Benchmark]

55 minutes ago, WVclimo said:

I'm waiting for Bluewave to embed a tweet about how fast of a flight it was from Tokyo to San Francisco, and then a 1994-2015 minus 2016-2025 250mb zonal wind graphic

[brooklynwx99]

Pacific jet is trending more equatorward towards mid-month, leading to a better wave break and more poleward ridging near AK… this makes sense given the MJO 

[SnowGoose69]

2 minutes ago, brooklynwx99 said:

Pacific jet is trending more equatorward towards mid-month, leading to a better wave break and more poleward ridging near AK… this makes sense given the MJO 

GEFS/GEPS in a snap shot mindset do not look great D14-16, but they're in the process it seems of evolving to something different.  A ton likely depends on where the MJO goes

[Daniel Boone]

9 minutes ago, 40/70 Benchmark said:

I'm waiting for Bluewave to embed a tweet about how fast of a flight it was from Tokyo to San Francisco, and then a 1994-2015 minus 2016-2025 250mb zonal wind graphic

You know he's working on something, lol.

[40/70 Benchmark]

11 minutes ago, Daniel Boone said:

You know he's working on something, lol.

He has a varied approach...may also be a Pacific SST chart along with sentence or six about how the models embellish phase 8 of the MJO in this "new, warmer climate".

[40/70 Benchmark]

I swear he has an alarm on his Iphone that is triggered whenever MJO812 smiles.

[MJO812]

[40/70 Benchmark]

1 minute ago, MJO812 said:

The larger test is mid month and onward.

[bncho]

lets listen to @MJO812 whenever the MJO might enter 8-1-2. it's literally in his name!

[brooklynwx99]

16 minutes ago, SnowGoose69 said:

GEFS/GEPS in a snap shot mindset do not look great D14-16, but they're in the process it seems of evolving to something different.  A ton likely depends on where the MJO goes

I agree that they don’t look as good… given the MJO progression, I feel like the EPS makes more sense. we’ll see

[40/70 Benchmark]

2 minutes ago, brooklynwx99 said:

I agree that they don’t look as good… given the MJO progression, I feel like the EPS makes more sense. we’ll see

Given the progression of the reflection event coupled with a weakening MJO wave, the GEFS make more sense to me mid month. Re-consolidating PV and developing PT regime.

[TheClimateChanger]

How's the weather looking in Ann Arbor on Saturday? Hearing rumors of snow for The Game?

[leo2000]

26 minutes ago, 40/70 Benchmark said:

Given the progression of the reflection event coupled with a weakening MJO wave, the GEFS make more sense to me mid month. Re-consolidating PV and developing PT regime.

The data seems to show though that this SSW event is a combined reflective-absorptive sudden stratospheric warming event. The reflection phase allows for the Alaskan Ridge and a positive AO and positive NAO in the near term. 

• Absorbing Phase: Subsequently, the stratosphere switches to an absorbing state, where it absorbs the upward wave energy, leading to a breakdown or weakening of the polar vortex. This absorption phase causes downward propagation of anomalous winds and is typically associated with a negative phase of the AO/NAM, leading to an increased likelihood of cold air outbreaks in mid-latitudes, particularly across North America and Eurasia. 

 

 

Tropospheric Impacts

The distinct phases of a combined event lead to a sequence of different weather impacts on the Earth's surface: 

• Near-term (Reflective Phase): Stronger westerlies and an active storm track across northern Europe may be observed, with temporary ridging in the North Pacific.
• Medium-term (Absorptive Phase): Increased pattern uncertainty emerges as the vortex breaks down, typically leading to the negative AO pattern and potential severe winter cold in mid-latitude regions. 

From Met Jens Bonewitz 

Stratospheric Update: hashtag#Potential Combined Reflective-Absorptive hashtag#SSW Developing!
Following yesterday's discussion (link: https://lnkd.in/egEFCFuq), models continue to indicate persistent hashtag#wave-1 forcing on the stratospheric polar vortex (SPV) extending into December—this time driven primarily by an intensifying hashtag#Aleutian Low.


We may be witnessing a combined or consecutive reflective-absorptive hashtag#SSW event. As discussed in the recent hashtag#Hannachi et al. (2025) paper, these complex events occur when upward propagating planetary waves first reflect off the disturbed vortex (creating negative heat fluxes that temporarily strengthen the SPV and accelerate the polar jet), before subsequently being absorbed, leading to vortex breakdown and downward wave activity flux propagation to the troposphere.

Expected hashtag#Tropospheric Response:
Near-term (into early hashtag#December):
hashtag#Pacific: Temporary Alaskan Ridge (AkR) development;
N Atlantic: Positive AO/NAO as reflected waves accelerate the jet stream—stronger westerlies and active storm track across northern EuropMedium-term (mid-late December):
Increasing pattern uncertainty as absorption phase dominates.
Downward coupling from the disturbed SPV likely triggers AO/NAO trend reversal. Enhanced (negative) blocking potential across Atlantic-European sector.

Key hashtag#Uncertainty:
The timing and magnitude of stratosphere-troposphere coupling in consecutive wave forcing events remains highly non-linear. While the ~60-day lag framework provides guidance, the volatile nature of this setup challenges deterministic forecasts beyond 2-3 weeks.

hashtag#Graphics (attached):
Time-height evolution of max.wave-1 height amplitude showing sustained and intense forcing in the upper and into the middle stratosphere (1-10 hPa) from late November through early December; source, incl.latest hashtag#forecast: https://lnkd.in/esD7gEtP. The persistent high-amplitude wave activity (>1500-1900 gpdm in the upper stratosphere) represents the continuous pressure on the polar vortex—key driver for the potential reflective-absorptive hashtag#SSW sequence.

Additional Context: 500 hPa hashtag#GFS forecast (30 Nov) showing the main tropospheric driver: intense hashtag#Aleutian Low. Note the deep low pressure system over the North Pacific providing upward wave forcing into the stratosphere.

Additional diagnostics:
https://lnkd.in/eM2nHteb
https://lnkd.in/eXr7cGtG

[MJO812]

27 minutes ago, 40/70 Benchmark said:

Given the progression of the reflection event coupled with a weakening MJO wave, the GEFS make more sense to me mid month. Re-consolidating PV and developing PT regime.

But the MJO is forecast to spend 7 to 10 days in phase 8. Im not sure if its going to be warm mid month. I can see a slight warmup but nothing lasting 

[Daniel Boone]

46 minutes ago, 40/70 Benchmark said:

Given the progression of the reflection event coupled with a weakening MJO wave, the GEFS make more sense to me mid month. Re-consolidating PV and developing PT regime.

Yeah, the reflection thing is a concerning Factor for sure. As mentioned earlier, it will make for an interesting forecast period with the MJO in cold Phases.

[LakePaste25]

The effects of the SSW look to completely decouple from the surface (for now). 

 

[stadiumwave]

 

https://x.com/webberweather/status/1993264759794282993?t=BTUYDs0rjkTSzBtZFlACrg&s=19

[MJO812]

[donsutherland1]

A colder pattern is now poised to develop in the Upper Midwest and Great Lakes Region.

The odds of a moderate (4" or above) to perhaps significant snowfall (6" or above) in Chicago Saturday into Sunday has increased. The daily record snowfall for November 29-30 is as follows:

November 29: 3.0", 1942
November 30: 3.0", 1907

Those 3.0" amounts are also the two-day records for November 29-30. Even if the daily mark isn't set on either day, the two-day figure for November 29-30 will likely be broken. In the wake of the storm, Chicago will likely have its snowiest fall since 2019 when 8.3" of snow was recorded. 

The snow should then spread into Detroit, Windsor, and Toronto Saturday night and Sunday. 
 

[so_whats_happening]

6 hours ago, 40/70 Benchmark said:

Given the progression of the reflection event coupled with a weakening MJO wave, the GEFS make more sense to me mid month. Re-consolidating PV and developing PT regime.

I would put the warm up around the week of christmas (unfortunately) and into the new year as of now. The MJO is in no real hurry so we may not get into 1/2 until January but start the warm up process at the tail-end of the potential phase 8.

Going to be a tough forecast for December in the temp anomaly contest thread.

[Krs4Lfe]

20 minutes ago, so_whats_happening said:

I would put the warm up around the week of christmas (unfortunately) and into the new year as of now. The MJO is in no real hurry so we may not get into 1/2 until January but start the warm up process at the tail-end of the potential phase 8.

Going to be a tough forecast for December in the temp anomaly contest thread.

Yes, absolutely it looks like most of the month will be pretty cold for much of the northern tier, from the northern Rockies through the Great Lakes and over to northern New England. But it seems like there will be a temperature battle zone across the rest of the northeast, the mid Atlantic, and the lower Midwest. Anywhere south of there looks to be pretty above average for most of December. In terms of storms and snows, it is bad to straddle the gradient in December because the average temperature for December is usually pretty conducive for snowfall, so being right around the average mark is not a bad place to be in. However, With a fast pacific jet, it becomes likelier that storms will either cut or become too suppressed. But in terms of strictly discussing temperature anomalies, our area seems to be in an average or slightly colder than average December.

[MJO812]

46 minutes ago, so_whats_happening said:

I would put the warm up around the week of christmas (unfortunately) and into the new year as of now. The MJO is in no real hurry so we may not get into 1/2 until January but start the warm up process at the tail-end of the potential phase 8.

Going to be a tough forecast for December in the temp anomaly contest thread.

Phase 8 /1 isnt warm 

 

[so_whats_happening]

3 minutes ago, MJO812 said:

Phase 8 /1 isnt warm 

 

[MJO812]

6 minutes ago, so_whats_happening said:

Is this for a weak La Nina? We have to see whats going to happen because next week was supposed to be warm and now look.

 

 

[so_whats_happening]

Just now, MJO812 said:

Is this for a weak La Nina? We have to see whats going to happen because next week was supposed to be warm and now look.

 

 

It is based on RMM phases not specific to La Nina or El Nino. Phase 8/1 doesn't become as conducive until we head into January and February for the east. I wouldn't expect blazing temps but I certainly wouldn't expect downright frigid outside of the colder period until about mid December/3rd week.

Still feel pretty confident in the warming potential as we move into christmas week and the new year. Surely things can change and it will be interesting to see if it does but overall I would expect near normal through much of the east with above normal across the SE.

The true test will be what happens with the December 2nd/3rd system and how that sets up. We will be able to see if the models are overzealous in either direction with respect to the SER or cold pressing into SE Canada.

[MJO812]

6 hours ago, so_whats_happening said:

It is based on RMM phases not specific to La Nina or El Nino. Phase 8/1 doesn't become as conducive until we head into January and February for the east. I wouldn't expect blazing temps but I certainly wouldn't expect downright frigid outside of the colder period until about mid December/3rd week.

Still feel pretty confident in the warming potential as we move into christmas week and the new year. Surely things can change and it will be interesting to see if it does but overall I would expect near normal through much of the east with above normal across the SE.

The true test will be what happens with the December 2nd/3rd system and how that sets up. We will be able to see if the models are overzealous in either direction with respect to the SER or cold pressing into SE Canada.

Phase 8 and Phase 1 are cold in negative enso years.

 

[bluewave]

15 hours ago, 40/70 Benchmark said:

I'm waiting for Bluewave to embed a tweet about how fast of a flight it was from Tokyo to San Francisco, and then a 1994-2015 minus 2016-2025 250mb zonal wind graphic

These long range OP runs can be very pretty. You can see a very broad -PNA trough developing in the ensemble means. Ongoing tug of war between the competing forcing influences

On one hand you have the forcing near the Maritime Continent causing the -PNA trough. The 2nd factor is the forcing over the Western Hemisphere trying to build a ridge bridge over the top from Northern Greenland to the -WPO ridge.

I suspect this split forcing is why we are getting a composite blend very long range between a Phase 6-7-8 look. The RMMS may try to slow the progression on the 7-8 border in response to split forcing.

So at this point I would say early December will feature a broad gradient type pattern with cold across the Northern tier.

Mid month will depend on the progression of the forcing. if the ridge bridge over the top wins out, then we will know a phase 8 is trying to take hold.

If the -PNA and +EPO become more dominant and the trough pulls back to the west, then we will know the forcing near the Maritime Continent is having a greater influence. 

Recent experience has favored the 2nd option of a relaxation of the pattern mid to late month. If this doesn’t happen, then we’ll know something new is taking place which we haven’t seen in a while. 
 

 

 

[snowman19]

15 hours ago, 40/70 Benchmark said:

Given the progression of the reflection event coupled with a weakening MJO wave, the GEFS make more sense to me mid month. Re-consolidating PV and developing PT regime.

It’s becoming more and more obvious where this is heading, despite the run to run changes on the long range ensembles….the stratospheric warming/wave reflection event looks to stay completely decoupled from the troposphere, then the SPV reconsolidates and strengthens quickly going into mid-late December. You, @so_whats_happening @donsutherland1 and @bluewave did a very good job explaining the expected MJO progression. Once we get towards mid-December, it is looking very likely that the Alaskan ridge regime retrogrades to an Aleutian ridge regime, the EPO goes +, a healthy -PNA pops and the SE ridge pumps

[Terpeast]

19 minutes ago, bluewave said:

These long range OP runs can be very pretty. You can see a very broad -PNA trough developing in the ensemble means. Ongoing tug of war between the competing forcing influences

On one hand you have the forcing near the Maritime Continent causing the -PNA trough. The 2nd factor is the forcing over the Western Hemisphere trying to build a ridge bridge over the top from Northern Greenland to the -WPO ridge.

I suspect this split forcing is why we are getting a composite blend very long range between a Phase 6-7-8 look. The RMMS may try to slow the progression on the 7-8 border in response to split forcing.

So at this point I would say early December will feature a broad gradient type pattern with cold across the Northern tier.

Mid month will depend on the progression of the forcing. if the ridge bridge over the top wins out, then we will know a phase 8 is trying to take hold.

If the -PNA and +EPO become more dominant and the trough pulls back to the west, then we will know the forcing near the Maritime Continent is having a greater influence. 

Recent experience has favored the 2nd option of a relaxation of the pattern mid to late month. If this doesn’t happen then we’ll know something new is taking place which we haven’t seen in a while. 
 

 

 

It will be interesting to see whether this split forcing, if it happens, is a continuation of the VP standing wave over the MC, or is a second wave propagating eastward from MJO 6>7>8>1. There is agreement that the first (current) wave is going to propagate into 8 and 1 in the coming days (according to both GEFS and EPS hovmoller charts), which makes sense as we're already tracking some wintry threats on the way next week. 

(and when I say wintry threats, I'm not saying it's going to snow imby, just talking generally over a broad area in the E and NE)