2026 ENSO Updates= CPC will use RONI / 1/26/26 update= Niño 3.4 at -0.3C

[cycloneye]

Remains a potent WWB on the models. Looks like it'll start this week and likely continue until the end of the month.

http://www.atmos.albany.edu/student/ventrice/real_time/timeLon/u.anom.30.5S-5N.gif

Is the WWB breaking apart? That CPC 75% of Neutral in the January-March timeframe may not happen.

[mixedDanilo.E]

WWB is happening right now but I'll be honest (and the post above me mentions this), but they don't look as strong and as menacing as people were talking about a week or 2 ago. And afterwards, marginal trades return to the EQ pacific. It's definitely gonna take more in order to get a full blown El Nino, even though it's more likely than not going to happen at some point this year. I honestly wonder if some of the models may be slightly over excited about the El Nino right now, especially the euro since it's showing like a strong event, and unless we have a massive WWB next month or March, I'm not sure if that is going to happen right now.

[Category5Kaiju]

Remains a potent WWB on the models. Looks like it'll start this week and likely continue until the end of the month.

http://www.atmos.albany.edu/student/ventrice/real_time/timeLon/u.anom.30.5S-5N.gif

Is the WWB breaking apart? That CPC 75% of Neutral in the January-March timeframe may not happen.

Looks like it is. I still think this past WWB was instrumental in helping us depart the cool neutral territory that we were in and will ultimately ease our way into El Nino later on. But I do think some of the predictions from last week and even several weeks ago may have been a tad bit too overzealous in thinking that we would rapidly enter neutral and that a strong El Nino is guaranteed. You need some exceptional coupling and a robust series of WWBs and warming to get remotely close to strong El Nino status (and, hence why in the grand scheme of things, weak or moderate El Ninos are more common than strong or very strong El Ninos).

Let's see how the warming process goes in the coming months and how much they're interrupted by trades or not.

[Kingarabian]

So although this WWB was supposed to be a bit more significant it will still likely impact the subsurface. I would pay close attention to the subsurface and see if warmer anomalies develop. A WWB in late February/March will more than likely trigger an El Nino. Right now almost everything is pointing towards an El Nino.

[cycloneye]

So although this WWB was supposed to be a bit more significant it will still likely impact the subsurface. I would pay close attention to the subsurface and see if warmer anomalies develop. A WWB in late February/March will more than likely trigger an El Nino. Right now almost everything is pointing towards an El Nino.

Is easy to see where things are going in this loop.

[cycloneye]

 https://x.com/cyclonicwx/status/2013107440066142389

[mixedDanilo.E]

So although this WWB was supposed to be a bit more significant it will still likely impact the subsurface. I would pay close attention to the subsurface and see if warmer anomalies develop. A WWB in late February/March will more than likely trigger an El Nino. Right now almost everything is pointing towards an El Nino.

Is easy to see where things are going in this loop.

https://i.imgur.com/Q8i1BJg.gif

These next few weeks will be very important in terms of evolution toward an El Nino. If we get these WWB's to be more consistent and long lasting, El nino will probably already begin to develop by late spring/summer, and we'll probably end up with a decently strong El Nino. If not, and instead we get situations like this WWB that happen initially but don't sustain, then we might see the event get delayed, and as a result, we will probably end up with a weak El nino. I think it will also be important to see how warm the Atlantic gets, as according to some the 2026 factors/indicators thread, there is a chance that an Atlantic Nino may form this year, and that tends to stunt a warm ENSO event.

[cycloneye]

For the members who know about this, have a question. The Southern Hemisphere has been very active so far with ACE well above average. https://tropical.atmos.colostate.edu/Realtime/

Being very active has an effect on ENSO?

[Dean_175]

For the members who know about this, have a question. The Southern Hemisphere has been very active so far with ACE well above average. https://tropical.atmos.colostate.edu/Realtime/

Being very active has an effect on ENSO?

Not a leading indicator, but sometimes a strong WWB can help generate tropical cyclones- sometimes on both sides of the equator. As for an above active season in itself being a harbinger of El Nino: that isn't a thing as far as I am aware. The dynamics at the equator are more important than what happens in other parts of the tropics.

[cycloneye]

The plume of ENSO models of January was updated today and the average mean of the dynamic models have weak El Niño for ASO.

[Kingarabian]

Over the WPAC, slower trades will continue entering February.

[Dean_175]

While it is still a wait and see, GFS is now showing a fairly sizable WWB first week of February (as of the date of this post).

[cycloneye]

 https://x.com/MJVentrice/status/2012491486898659734

[cycloneye]

This animation is from August thru January 19. Look how the warm waters have been expanding to the east while the colder waters shrink.

[cycloneye]

Breaking News

CPC will begin to use the RONI data to calculate the sst anomalies. I think our friend LarryWx was the one promoting this for a long time and here it is starting on Febuary 1.

https://www.weather.gov/media/notificat ... ve_ONI.pdf

Public Information Statement Implementing a Relative Oceanic
Niño Index effective February 1, 2026

The National Centers for Environmental Prediction (NCEP) Climate
Prediction Center (CPC) informs the public of the shift to a Relative
Oceanic Niño Index for the official monitoring and prediction of the El
Niño-Southern Oscillation (ENSO) phenomenon, effective February 1, 2026.
ENSO is the leading pattern of year-to-year climate variability, and
plays an important role in subseasonal to seasonal variations in
temperature, precipitation, storm tracks, hurricane activity, and other
impactful variables in the weather-climate system.
When implemented, NCEP CPC will define El Niño (La Niña) as a relative,
positive (negative) mean SST anomaly of 0.5 degrees C or greater over 3
consecutive months in the Niño 3.4 region of the central Pacific Ocean (5
degrees N to 5 degrees S and 120 degrees W to 170 degrees W). This
anomaly is computed by subtracting the average SST anomaly of the global
tropics (20 degrees N to 20 degrees S) from the Niño 3.4 regional
anomaly. After the subtraction, the relative index is rescaled to match
the amplitude of the traditional index.
The Relative Oceanic Niño Index (RONI) is defined as the three month
running average of the relative Niño 3.4 index. Historical El Niño and
La Niña events will be categorized based on this index, specifically when
there are five or more consecutive, overlapping three-month seasons where
the RONI is greater than 0.5C (El Niño) or less than -0.5C (La Niña).
The RONI is visually very similar to the traditional ONI, so users can
use it in the same way as they would the traditional ONI.
This proposed change will have two primary benefits for ENSO monitoring
and prediction: 1) the relative sea surface temperature index better
identifies current and past El Niño and La Niña events because it is less
sensitive to the chosen base climatology period. This allows for
comparison of events across the lengthy climate record. 2) A relative
index is more related to changes in rainfall over the tropical Pacific
than the traditional index. Over the past year, the relative SST index
was better aligned with the intensity of rainfall anomalies and
circulation changes associated with the ENSO phenomenon. It is the
change in tropical rainfall and heating that ultimately drives the

[cycloneye]

CPC weekly update of 1/26/26 has Niño 3.4 up to -0.3C and the depth continues to get warmer.

https://www.cpc.ncep.noaa.gov/products/ ... ts-web.pdf

[Dean_175]

Breaking News

CPC will begin to use the RONI data to calculate the sst anomalies. I think our friend LarryWx was the one promoting this for a long time and here it is starting on Febuary 1.

https://www.weather.gov/media/notificat ... ve_ONI.pdf

Makes sense, particularly in the context of climate change and the intrinsic variability of ENSO(the La Ninas of the early 2020s adjusted the base state that is updated every 5 years such that 2023 now has two trimonthlies of >2.0C with one of them being 2.1C despite a relative lack of coupling and a 2015 peak adjusted to 2.8C, which I feel is a little high even for that year). Meanwhile, 2024 and 2025 do not qualify as La Nina based on raw ONI despite the atmosphere indicating otherwise. RONI for 2025 event should come in around -0.7 or -0.8C-perhaps even -0.9C

[cycloneye]

Historic data of RONI since 1952 has 26 El NIño events and 28 La NIñas.

https://ggweather.com/enso/roni.htm

[Kingarabian]

GFS going crazy again with another extreme WWB

[cycloneye]

GFS going crazy again with another extreme WWB

Boom.