2025-2026 ENSO

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15 hours ago, leo2000 said:

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

I don't care how much crap can be dug up from AI, the strat stuff is pretty useless.

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56 minutes ago, MJO812 said:

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

 

The MJO is but one factor that can either constructively, or deconstructivity interfere with baseline forcing.....what you are implying is akin to saying that I jog 3x weekly, so I know I'm very healthy....come to find out, I also smoke 6 packs a week, inhale MacDonalds 3x daily and have casual unprotected sex with one-legged prostitutes on a nightly basis.

[bluewave]

5 minutes ago, Terpeast said:

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)

I suspect this split forcing is the reason for the volatility that we have been seeing in the models for the first 10 days of December. Models struggle with the placement of features when there are multiple areas of forcing. My only guess that I made earlier for December is that we will have a weaker -PNA and colder Canada than last year. 

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2 minutes ago, bluewave said:

I suspect this split forcing is the reason for the volatility that we have been seeing in the models for the first 10 days of December. Models struggle with the placement of features when there are multiple areas of forcing. My only guess that I made earlier for December is that we will have a weaker -PNA and colder Canada than last year. 

Absolutely this.

[EasternLI]

Really good recent paper here when considering this stratosphere wave reflection event. I feel like this influence is taking control of things for a bit. And models are trying to resolve this influence. As it does fit in with what we're seeing, and what models are doing. Which, if it is, then begs the question. What takes over once the life cycle runs its course? And when? Since the end dates apparently vary (but are typically ~2 weeks) and aren't very well understood. It's interesting. Probably a future case study. 

 

Dynamics of stratospheric wave reflection over the North Pacific

https://wcd.copernicus.org/articles/6/521/2025/

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7 hours ago, so_whats_happening said:

Where did you pull those graphics from?

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9 minutes ago, EasternLI said:

Really good recent paper here when considering this stratosphere wave reflection event. I feel like this influence is taking control of things for a bit. And models are trying to resolve this influence. As it does fit in with what we're seeing, and what models are doing. Which, if it is, then begs the question. What takes over once the life cycle runs its course? And when? Since the end dates apparently vary (but are typically ~2 weeks) and aren't very well understood. It's interesting. Probably a future case study. 

 

Dynamics of stratospheric wave reflection over the North Pacific

https://wcd.copernicus.org/articles/6/521/2025/

That is the progression I expect in January.

[snowman19]

That is the progression I expect in January.

You are expecting the flip to happen mid-late January still?

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4 minutes ago, snowman19 said:

You are expecting the flip to happen mid-late January still?

Yea....I expected a non-reversal warming early in the season, and then another reflection event in mid January, followed up a major SSW complete with reversal in February.