2025-2026 ENSO

[GaWx]

 I’m still looking for strat. zonal wind data for 1983 and 1989. In the meantime, I did find the following graph, which is of 65N to 90N zonal mean temperatures at 10 mb in 1988 and 1989. Look on the far right: although there was no major SSW in any of the tables I look at (meaning no reversal of zonal winds at 10 mb), you can see there still was a bit of a stratospheric warming spike centered on ~Dec 1st of 1989 to near a record high for that date: 

https://www.cpc.ncep.noaa.gov/products/stratosphere/temperature/archive/10mb9065_1989.gif

——————

 This is even more evident further up at 5 mb and at 2 mb:

5 mb: 15C spike warming centered near 12/1/1989:

https://www.cpc.ncep.noaa.gov/products/stratosphere/temperature/archive/05mb9065_1989.gif

—————

2 mb: 15C spike warming centered near 12/1/1989:

https://www.cpc.ncep.noaa.gov/products/stratosphere/temperature/archive/02mb9065_1989.gif

[donsutherland1]

When it comes to sudden stratospheric warming events (SSWEs) or major stratospheric warming events (MSWEs), these events can be a response to strong blocking (bottom-up), which often reinforces and extends the blocking. They can also be top-down events that lead to a downward-propagating tropospheric response. 

Typically, there is approximately a 10-20-day lag, where the NAO/AO move toward and into a negative state. This blocking can then persist for 30 days and longer, with some fluctuations. 

Tropospheric responses to vortex-splitting events are often stronger than those for displacement events. However, more often than not, the larger portion of the split vortex winds up in Eurasia and the smaller one moves into North America.

So, if the sudden or major stratospheric warming event occurs in the closing days of this month, its impact on North America would probably start to be seen near mid-December +/- few days. 

Right now, a major event with a wind reversal isn't assured. 

 

 

[FPizz]

3 hours ago, snowman19 said:

The news is comical right now. The bad, false info about SSWEs they are putting out is astonishing. A real disservice honestly. They don’t even talk about the lag effect and are hyping an ice age coming up the end of this month

The ice age hype is coming from the usual hysteria crowd.  The headline today is Gulf Stream will shut down, leading to oceans rising and an ice age.  Yeah, figure that one out.  It is all about clicks and if you are a scientist looking for pal review, funding, which now is the same as clicks. 

[stadiumwave]

3 hours ago, snowman19 said:

The news is comical right now. The bad, false info about SSWEs they are putting out is astonishing. A real disservice honestly. They don’t even talk about the lag effect and are hyping an ice age coming up the end of this month

 

There can be immediate affects on the troposphere if the SPV & troposphere are strongly coupled which does not appear to be the case at the moment. If it gets immediately cold in early DEC it is not from the affects of the SSWE. And obviously there are no guarantees of how the SSWE later shakes out in the troposphere, we can only use analogs to guess. 

[kazimirkai]

22 hours ago, EasternLI said:

Yeah, that will be interesting to watch evolve. Extended range EPS and GEFS are advertising this WWB to push out to the dateline. Which has proven difficult to do in other recent La Niña years. So I'm curious to see how this one goes as we move into December. 

Yeah my professor was highlighting the off-the-scale wind anomaly within the last few days. He does think that the MJO will wrap back around before reaching 8 and usher in a more central US trough for the latter part of December. Fairly confident that the beginning will be cold though.

[stadiumwave]

21 minutes ago, donsutherland1 said:

When it comes to sudden stratospheric warming events (SSWEs) or major stratospheric warming events (MSWEs), these events can be a response to strong blocking (bottom-up), which often reinforces and extends the blocking. They can also be top-down events that lead to a downward-propagating tropospheric response. 

Typically, there is approximately a 10-20-day lag, where the NAO/AO move toward and into a negative state. This blocking can then persist for 30 days and longer, with some fluctuations. 

Tropospheric responses to vortex-splitting events are often stronger than those for displacement events. However, more often than not, the larger portion of the split vortex winds up in Eurasia and the smaller one moves into North America.

So, if the sudden or major stratospheric warming event occurs in the closing days of this month, its impact on North America would probably start to be seen near mid-December +/- few days. 

Right now, a major event with a wind reversal isn't assured. Also, the warming and wind reversal appear to be centered mainly south of 60N vs. the 60N-90N region that is conducive to triggering or extending Arctic blocking. Warming events centered south of 60N often do not produce the same downward-propagating tropospheric impacts of those that occur in the 60N-90N region. That's an important detail that will need to be considered. 

 

 

My 4 weeks post was simply looking at the previous years with early warming events, looking at the following weeks & in those few years this has occurred, it appeared to be around 4 weeks the troposphere was clearly being affected by the event, which I found interesting. 

Great post Don & much needed...as usual! 

[GaWx]

Today’s 2 week GEFS and EPS MJO progs are in very good agreement on the MJO being hung up near the 6/7 border with moderate intensity:

GEFS:

EPS:

 

 Here’s yesterday’s (11/12/25) extended EPS (these always come out at this site a day later): after the near 2 week long stall near the 6/7 border, it crawls through 7 and then barely into 8 with a trajectory that suggests it might collapse into within the circle/weak amplitude soon afterward. But keep in mind that should it actually occur, a weak amplitude doesn’t at all necessarily mean mild in the E US as weaker MJO on the left side is often associated with cold based on analyses I’ve done and posted here plus charts I’ve seen from others: just outside the circle phase 8 in Dec like this shows has sometimes been associated with quite cold in the E US:

[PhiEaglesfan712]

12 hours ago, George001 said:

I was curious so I looked into it a bit. Following a multi year cold ENSO stretch when it did go warm ENSO, 9/12 times the follow up Nino was a moderate or stronger event. I would bet against a super Nino though, given we just had a +2 ONI peak El Niño 2 years ago. Gun to head, I would bet on our next El Niño being either next year or the year after, and being similar in strength to 02-03 or 09-10. 

1949-51 la nina -> 1951-52 moderate el nino (yes, also continued in 1952-54)

1954-57 la nina -> 1957-58 strong el nino (yes, also continued in 1958-59)

1970-72 la nina -> 1972-73 super el nino (yes)

1974-76 la nina -> 1976-77 & 1977-78 moderate el nino (yes)

1983-85 la nina -> 1986-88 strong el nino (yes)

1988-90 la nina -> 1991-92 strong el nino (yes)

1998-2001 la nina -> 2002-03 moderate el nino (yes)

2007-09 la nina -> 2009-10 strong el nino (yes)

2010-12 la nina - no el nino in 2012-13 or 2013-14 (though we did get a super el nino in 2015-16)

2016-18 la nina -> 2018-19 weak el nino (no)

2020-23 la nina -> 2023-24 strong el nino (yes)

So, within 2 years of a multi-year cold ENSO (at least one year la nina), we have:

1 no el nino (and this one eventually produced a strong el nino)

1 weak el nino

3 moderate el nino

5 strong el nino

1 super el nino

Plus, 4 of these events were multi-year el ninos (1951-54, 1957-59, 1976-78, and 1986-88).

[so_whats_happening]

59 minutes ago, snowman19 said:

I took BAMWX’s word for it. Lol I guess they are mistaken?

 

 

 

 

Oh man I feel like we go through this every winter. Warmings occur all the time this is not a new occurrence by any means. I do like to see there is some connection through the layers to show maybe some extended connection as we go through time but anything past 240hr is typically a crapshoot call even with something like the stratosphere which doesn't tend to have too much change.

38 minutes ago, donsutherland1 said:

I agree. Hopefully, CPC will start using RONI as its official measure. In any case, the relationship holds true with ONI or RONI.

My biggest issue with the use of RONI being implemented what if for some reason this process does actually switch up and ONI does become more representative than RONI are we going to switch back to using ONI data as reliable indication of Nina/Nino severity?

To me RONI is like the equivalency of saying well if we take out the warming of the last 50-100 years in something like air temperature (just an example) to show that in fact temps would have been cooler during this time period to me means nothing. Ok we have deduced that it is warmer now than in the past.

The processes that are involved with ENSO/ IOD/ PDO/ AMO have not seemingly changed, they all still evolve in the same manner. Are we trying to say that RONI is showing enhancement of La Ninas specifically? Are you and bluewave stating that because RONI showed -1.12 last winter for DJF that the winter acted like a moderate La Nina versus cold neutral? I mean just taking a quick glance at years of similar ONI where we never officially hit Nina status by measurements (some awfully close like last year). I did not match scales so forgive me on that. Only difference I see is a slightly more poleward low position in the pacific. I feel this is more of a PDO situation.

 

[kazimirkai]

3 minutes ago, GaWx said:

Today’s 2 week GEFS and EPS MJO progs are in very good agreement on the MJO being hung up near the 6/7 border with moderate intensity:

GEFS:

EPS:

 

 Here’s yesterday’s (11/12/25) extended EPS (these always come out at this site a day later): after the near 2 week long stall near the 6/7 border, it crawls through 7 and then barely into 8 with a trajectory that suggests it might collapse into within the circle/weak amplitude soon afterward. But keep in mind that should it actually occur, a weak amplitude doesn’t at all necessarily mean mild in the E US as weaker MJO is often associated with cold based on analyses I’ve done plus charts I’ve seen from others:

Well the low-frequency background state shows low heights in the east during the time period where MJO is most likely not projecting so the pattern is likely to stay generally seasonal. I wouldn't expect a massive warmup or anything but more of a moderation

[so_whats_happening]

1 hour ago, GaWx said:

 I’m still looking for strat. zonal wind data for 1983 and 1989. In the meantime, I did find the following graph, which is of 65N to 90N zonal mean temperatures at 10 mb in 1988 and 1989. Look on the far right: although there was no major SSW in any of the tables I look at (meaning no reversal of zonal winds at 10 mb), you can see there still was a bit of a stratospheric warming spike centered on ~Dec 1st of 1989 to near a record high for that date: 

https://www.cpc.ncep.noaa.gov/products/stratosphere/temperature/archive/10mb9065_1989.gif

——————

 This is even more evident further up at 5 mb and at 2 mb:

5 mb: 15C spike warming centered near 12/1/1989:

https://www.cpc.ncep.noaa.gov/products/stratosphere/temperature/archive/05mb9065_1989.gif

—————

2 mb: 15C spike warming centered near 12/1/1989:

https://www.cpc.ncep.noaa.gov/products/stratosphere/temperature/archive/02mb9065_1989.gif

This might help you out

https://acd-ext.gsfc.nasa.gov/Data_services/met/ann_data.html

[kazimirkai]

1 hour ago, GaWx said:

There are no official Nov or Dec major SSWs based on reversals at 10 mb for any of 1983, 1989, and 2000.

To be fair if you read this closely, BAMwx isn’t explicitly saying that there was an early major SSW in any of those 3 years (if they were they’d be wrong):

A few of these years were absolutely blockbuster in December. Chances to replicate the intensity of cold in years like 2000, 1989 and 1983 are unlikely, but there is strong support notable cold the first half of December setting up.

 That’s not to say that the SPV wasn’t weak. Despite no reversal, 2000 was quite weak mid-Nov through Dec with a low of +4 to +5 m/s in late Nov as per the chart below: (I don’t have these charts for 1983 and 1989….does anyone else have a link to them?):

It does seem like this event is increasingly projected to pretty quickly rebound by mid month Dec. We'll see if the MJO has anything up its sleeve regarding a 2000 situation 

[40/70 Benchmark]

3 minutes ago, kazimirkai said:

It does seem like this event is increasingly projected to pretty quickly rebound by mid month Dec. We'll see if the MJO has anything up its sleeve regarding a 2000 situation 

It should. The conjecture about locking through January is silly.

[donsutherland1]

29 minutes ago, so_whats_happening said:

Oh man I feel like we go through this every winter. Warmings occur all the time this is not a new occurrence by any means. I do like to see there is some connection through the layers to show maybe some extended connection as we go through time but anything past 240hr is typically a crapshoot call even with something like the stratosphere which doesn't tend to have too much change.

My biggest issue with the use of RONI being implemented what if for some reason this process does actually switch up and ONI does become more representative than RONI are we going to switch back to using ONI data as reliable indication of Nina/Nino severity?

To me RONI is like the equivalency of saying well if we take out the warming of the last 50-100 years in something like air temperature (just an example) to show that in fact temps would have been cooler during this time period to me means nothing. Ok we have deduced that it is warmer now than in the past.

The processes that are involved with ENSO/ IOD/ PDO/ AMO have not seemingly changed, they all still evolve in the same manner. Are we trying to say that RONI is showing enhancement of La Ninas specifically? Are you and bluewave stating that because RONI showed -1.12 last winter for DJF that the winter acted like a moderate La Nina versus cold neutral? I mean just taking a quick glance at years of similar ONI where we never officially hit Nina status by measurements (some awfully close like last year). I did not match scales so forgive me on that. Only difference I see is a slightly more poleward low position in the pacific. I feel this is more of a PDO situation.

 

I see your point. The argument for RONI is that the overall warming of the Pacific is not temporary or cyclical.

The use of traditional ENSO metrics i.e., R3.4 anomaly, ONI, etc., has beenb contaminated by the overall warming of the Pacific. In their present form, El Niño events are amplified while La Niña ones are shown as weaker. As the warming continues, La Niña events could even be obscured. Winter 2024-2025 is one such case. It showed up as neutral-cold on ONI, but was a La Niña case according to RONI.

Some useful literature on the use of a relative index: 

https://iopscience.iop.org/article/10.1088/1748-9326/abe9ed

https://journals.ametsoc.org/view/journals/clim/37/4/JCLI-D-23-0406.1.xml

Australia's Bureau of Meteorology (BOM) has already made the switch to RONI. 

Here's a table from the article concerning the BOM's shift:

[PhiEaglesfan712]

Whether or not you use ONI or RONI, if you ignore what went on in Nino 1+2 last winter, then you're totally missing the picture. Last winter wasn't going to behave like a traditional la nina, or even a cold-neutral, with that warm eastern basin.

[donsutherland1]

2 minutes ago, PhiEaglesfan712 said:

Whether or not you use ONI or RONI, if you ignore what went on in Nino 1+2 last winter, then you're totally missing the picture. Last winter wasn't going to behave like a traditional la nina, or even a cold-neutral, with that warm eastern basin.

I agree. The analog cases I used consider ENSO Region 1+2.

[40/70 Benchmark]

9 minutes ago, donsutherland1 said:

I agree. The analog cases I used consider ENSO Region 1+2.

Modoki.

[donsutherland1]

The closest five analog PDO cases (based on RMSE) suggest that the PDO will likely rise during the winter, but remain negative. If one looked at the top 10 cases, just one (2010-11) showed the PDO rising above zero during the winter. That case ranked 10th in terms of RMSE. The October 2025 PDO value was -2.40.

[MJO812]

Interesting

[GaWx]

2 hours ago, donsutherland1 said:

When it comes to sudden stratospheric warming events (SSWEs) or major stratospheric warming events (MSWEs), these events can be a response to strong blocking (bottom-up), which often reinforces and extends the blocking. They can also be top-down events that lead to a downward-propagating tropospheric response. 

Typically, there is approximately a 10-20-day lag, where the NAO/AO move toward and into a negative state. This blocking can then persist for 30 days and longer, with some fluctuations. 

Tropospheric responses to vortex-splitting events are often stronger than those for displacement events. However, more often than not, the larger portion of the split vortex winds up in Eurasia and the smaller one moves into North America.

So, if the sudden or major stratospheric warming event occurs in the closing days of this month, its impact on North America would probably start to be seen near mid-December +/- few days. 

Right now, a major event with a wind reversal isn't assured. Also, the warming and wind reversal appear to be centered mainly south of 60N vs. the 60N-90N region that is conducive to triggering or extending Arctic blocking. Warming events centered south of 60N often do not produce the same downward-propagating tropospheric impacts of those that occur in the 60N-90N region. That's an important detail that will need to be considered. 

 

Thanks as always, Don.

 The weakest zonal winds/wind reversal on your bottom chart (Euro zonal wind forecast for 12Z on 11/22/25) actually are within 60-90N (blue shades) rather than south of 60N.

 For 60N at 10 mb, this actually shows a very weak wind of a mere +5 on 11/22 (and is dropping) and that’s still ~3 days before the EPS mean drops to 0.

[GaWx]

1 hour ago, so_whats_happening said:

This might help you out

https://acd-ext.gsfc.nasa.gov/Data_services/met/ann_data.html

Thanks for the link!

From there:

Nov/Dec 1983: SPV not even weak

 

————-
Nov/Dec 1989: SPV actually pretty strong

——————-

Nov/Dec 2000 no reversal but SPV quite weak with low ~+4 late Nov:

 

So, none of Novs/Decs 1983, 1989, and 2000 had a major SSW (reversal) though 2000 had a weak SPV.

@snowman19

[donsutherland1]

29 minutes ago, GaWx said:

Thanks as always, Don.

 The weakest zonal winds/wind reversal on your bottom chart (Euro zonal wind forecast for 12Z on 11/22/25) actually are within 60-90N (blue shades) rather than south of 60N.

 For 60N at 10 mb, this actually shows a very weak wind of a mere +5 on 11/22 (and is dropping) and that’s still ~3 days before the EPS mean drops to 0.

I screwed up on the last part. I had been looking at a lot of temperature charts and used the wrong scale when switching to winds. 

[GaWx]

19 minutes ago, donsutherland1 said:

I screwed up on the last part. I had been looking at a lot of temperature charts and used the wrong scale when switching to winds. 

No worries, Don! Very easy to do. I sometimes get them mixed up. Actually, at first, I didn’t see what I noticed with a second look.