2025 ENSO Updates

[Kingarabian]

Other than 2024, the atmosphere component of ENSO in general has been behaving closer to the current CPC ONI vs RONI over the past decade.

[USTropics]

Other than 2024, the atmosphere component of ENSO in general has been behaving closer to the current CPC ONI vs RONI over the past decade.

I would check out this recent research article - https://journals.ametsoc.org/view/journ ... 0406.1.xml. They went back and applied RONI to 1979 - 2022 and concluded this:

To establish that the relative Niño-3.4 index captures variability more strongly associated with seasonal ENSO teleconnections, we evaluated relationships with the global mean circulation and precipitation anomalies. ONI relationships with 200-hPa geopotential height are characterized by higher heights across most of the globe compared to the relative index. Also, a three-predictor regression with CO2, tropical mean SST, and the ONI as predictors reveals that the height pattern associated with the ONI, independent of the other two predictors, strongly resembles that of the relative ONI. This finding suggests that radiative effects, embedded within the CO2 and tropical mean SST influences, are leaking into the nonrelative index. Additionally, the pattern of tropical Pacific precipitation anomalies becomes sharper when a relative index is used. During their respective winter/spring seasons, the relative index describes about ∼5%–10% more precipitation variability over portions of the southern United States and eastern Australia. All considered, a relative SST index appears to better isolate the expected ENSO teleconnections, without mixing in signals from background climate change or low-frequency variability.

For some purposes, such as the prediction of seasonal temperature and precipitation, it is fundamental to consider lower-frequency climate changes and ENSO collectively. But for attribution and for monitoring of the ENSO phenomenon itself, it is problematic to have climate change incorporated within the Niño-3.4 index/ONI. Without an adjustment made to the traditional ENSO index, a periodic reshuffling of historically classified El Niño and La Niña events is likely to occur, which may not reflect baseline conditions experienced at the time of the event. This paper expands upon the initial work of van Oldenborgh et al. (2021) and further justifies the use and adoption of a relative SST index for monitoring and prediction. As they previously cautioned, in the future, if there are significant divergences between the tropical mean state and trends in the Niño indices, then this index will need to be re-evaluated.

It's definitely not a perfect solution (ONI can even outperform in the first part of the year) but it does provide a solution to a problem that isn't going away (i.e., global SSTs are not going to suddenly have a decline).

[cycloneye]

All four ENSO regions cooled on this CPC 4/14/25 update.

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

[cycloneye]

 https://x.com/AndyHazelton/status/1913259703062126910

[cycloneye]

 https://x.com/dmorris9661/status/1913544847593558332

[Kingarabian]

Very common in cool/warm neutral conditions. Nino 1+2 is pretty shallow and is prone to wild swings.

[Kingarabian]

NOAA and JMA both had the PDO warming a bit for March. +Anomalies east of Japan have taken a hit since December.

[cycloneye]

 https://x.com/BigJoeBastardi/status/1914106700472418781

[cycloneye]

CPC weekly 4/21/25 ENSO update has for a second week in a row, all regions going down.

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

[weeniepatrol]

IMO I definitely think relative indices will have an increasingly important role as time progresses. Much of Earths' variability (such as oceanic and atmospheric circulations) is driven by gradience in SSTs. So, as the broader Pacific continues to warm, less cold equatorial Pacific SSTs will receive the same Nina-esque atmospheric response since the gradience in SSTs would be comparable to the pre-AGW conditions of colder equatorial Pacific SSTs but a cooler broader Pacific.

This may partially be a reason why the 2023-4 El Nino exhibited an anemic atmospheric response (with a 140-ACE Atlantic season) relative to the magnitude of SSTAs (peak ONI of +2.0 in NDJ), and why the 2024-5 La Nina barely sustained -0.5 C SSTAs yet exhibited a robust longwave atmospheric response. Over the equatorial Pacific in particular, conditions such as OLR anomalies and trade wind anomalies have been reminiscent of a moderate-strong Nina, not a marginal weak one.

[cycloneye]

The plume of ENSO models stay in neutral thru ASO.

[USTropics]

These products are from Ben Noll's site - https://www.bennollweather.com/climate-graphics

Here is the full table of ONI forecasts over the next 6 months:


I do think (based on RONI), the atmosphere may exhibit similar teleconnections as a traditional cold neutral ENSO year during peak season:


As Kingarabian and others have stated, this would align with a more inactive EPAC.

[cycloneye]

Bye to El Niño Costero.

 https://x.com/BenNollWeather/status/1914677570249089449

[mixedDanilo.E]

No major wwb's indicated in the pacific on the EPS right on into May. Definitely not rushing toward any major ENSO event right now.

[weeniepatrol]

https://charts.ecmwf.int/streaming/20250422-2000/db/ps2png-worker-commands-595747cf5-dc2ml-6fe5cac1a363ec1525f54343b6cc9fd8-dtl96t8x.png

No major wwb's indicated in the pacific on the EPS right on into May. Definitely not rushing toward any major ENSO event right now.

Chances for any El Nino seem to be diminishing. As others have noted, ENSO sensitivity to intraseasonal forcing drops off a cliff after May. The Summer trade winds are coming, and with it the window for a warm ENSO event probably closing shut.

[weeniepatrol]

By the way, for March the PDO rose to -0.41. There have been zero positive monthlies during the entirety of the 2020s*; the last positive monthly was December 2019. Will we finally notch a positive reading?

* = it looks something like this:

[cycloneye]

The CPC weekly 4/28/25 update has 3.4 at dead neutral 0.0C. Niño 1+2 down to -0.3C.

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

[cycloneye]

 https://x.com/AndyHazelton/status/1916871013536506105