2026 ENSO Updates

[Ntxw]

MJO forecasts is looping back to the Pacific, and may loop back yet again. 200mb CHI charts show sinking motion returning to the MC region while re-igniting over the Pacific. Pretty good indicator background low frequency is shifting closer to El Nino mode.

[AJC3]

The first shoe has dropped and is from the BoM of Australia.

https://i.imgur.com/SNR3rQQ.jpeg

https://www.bom.gov.au/climate/ocean/outlooks/archive/20260328//plumes/sstOutlooks.rnino34.hr.png

https://www.bom.gov.au/climate/enso/?ni ... s=Overview

I'm not gonna lie to you, even though strong El Nino is looking more likely, I have a hard time believing we will get as as strong as the BoM forecasts, especially by September. What especially makes me want to partially throw this run out is a HUGE jump in the index from March to April. I'm sorry but I do not see that happening.

Since there's a dash between FEB-MAR, that makes me think that their MAR value (about -0.55C) is a hindcast/nowcast that was used to initialize that run of the ACCESS-S2, rather than an actual analyzed data point. That point on the graph doesn't even match their own NINO 3.4 value (-0.42C) shown in the text, and moreover, CPC's latest update from 30 MAR had that value as -0.3C. I know BoM/CPC have different ENSO thresholds, but is there also a fundamental difference in how actual ENSO values are calculated? In any event, if you plot the CPC value on the chart, then the BOM model change from MAR-APR doesn't look nearly as odd. Just some food for thought.



Caveat: There might be something I'm not taking into account about how the indices are calculated.

[DorkyMcDorkface]

I've learned a lot about ENSO over the past 5 years but I have a question: when was the last time we've had a strong Niño event so suddenly after another? Seems like they occur once every decade or so, but this time around we're getting two in rather quick succession. I also wonder because the last time it was understandable with a triple-dip moderate Niña event the first half of the 2020s but this time around we've had two weaker Niña events (according to RONI, ONI was nearly merely cool-neutral for 2024-25). What's the case this time around?

[Ntxw]

I've learned a lot about ENSO over the past 5 years but I have a question: when was the last time we've had a strong Niño event so suddenly after another? Seems like they occur once every decade or so, but this time around we're getting two in rather quick succession. I also wonder because the last time it was understandable with a triple-dip moderate Niña event the first half of the 2020s but this time around we've had two weaker Niña events (according to RONI, ONI was nearly merely cool-neutral for 2024-25). What's the case this time around?

One aspect we have to think about is that the warm pool over the western Pacific has been prolific in the 2020s. The warm water expanse has been incredible El Nino or La Nina. 2023-2024 did not fully disperse this warm pool. It's physics, if the bathwater is continuously hot, any shift will allow it to move despite what ENSO was. This is something we don't fully understand with global oceans warming rapidly. A theoretical idea one could ask, since 2023-24 did not fully behave like a traditional Nino, could it be reason why we're seeing a more traditional one form so close?

1963-64, and then 1965-66 had a moderate and strong Nino pretty quickly.

[cycloneye]

Astounding is the word for this.

 https://x.com/PaulRoundy1/status/2039726383719727485

[DorkyMcDorkface]

I've learned a lot about ENSO over the past 5 years but I have a question: when was the last time we've had a strong Niño event so suddenly after another? Seems like they occur once every decade or so, but this time around we're getting two in rather quick succession. I also wonder because the last time it was understandable with a triple-dip moderate Niña event the first half of the 2020s but this time around we've had two weaker Niña events (according to RONI, ONI was nearly merely cool-neutral for 2024-25). What's the case this time around?

One aspect we have to think about is that the warm pool over the western Pacific has been prolific in the 2020s. The warm water expanse has been incredible El Nino or La Nina. 2023-2024 did not fully disperse this warm pool. It's physics, if the bathwater is continuously hot, any shift will allow it to move despite what ENSO was. This is something we don't fully understand with global oceans warming rapidly. A theoretical idea one could ask, since 2023-24 did not fully behave like a traditional Nino, could it be reason why we're seeing a more traditional one form so close?

1963-64, and then 1965-66 had a moderate and strong Nino pretty quickly.

So would you say the accumulation of subsurface warmth in the Indo-Pacific Warm Pool is a byproduct of the three consecutive Niñas i mentioned + general warming of the oceans? I think the latter reason in particular could explain why a triple dip Niña event like 1998-2001 didn't result in a strong/super Niño in 2002-03 (was moderate and CPAC-based iirc). Perhaps if it occured nowadays in a warmer oceanic climate it might have?

[Ntxw]

I've learned a lot about ENSO over the past 5 years but I have a question: when was the last time we've had a strong Niño event so suddenly after another? Seems like they occur once every decade or so, but this time around we're getting two in rather quick succession. I also wonder because the last time it was understandable with a triple-dip moderate Niña event the first half of the 2020s but this time around we've had two weaker Niña events (according to RONI, ONI was nearly merely cool-neutral for 2024-25). What's the case this time around?

One aspect we have to think about is that the warm pool over the western Pacific has been prolific in the 2020s. The warm water expanse has been incredible El Nino or La Nina. 2023-2024 did not fully disperse this warm pool. It's physics, if the bathwater is continuously hot, any shift will allow it to move despite what ENSO was. This is something we don't fully understand with global oceans warming rapidly. A theoretical idea one could ask, since 2023-24 did not fully behave like a traditional Nino, could it be reason why we're seeing a more traditional one form so close?

1963-64, and then 1965-66 had a moderate and strong Nino pretty quickly.

So would you say the accumulation of subsurface warmth in the Indo-Pacific Warm Pool is a byproduct of the three consecutive Niñas i mentioned + general warming of the oceans? I think the latter reason in particular could explain why a triple dip Niña event like 1998-2001 didn't result in a strong/super Niño in 2002-03 (was moderate and CPAC-based iirc). Perhaps if it occured nowadays in a warmer oceanic climate it might have?

Something of that nature would be a thought. 1997 super El Nino was also very efficient in dispersing the WPAC warm pool both oceanic and atmospherically whereas 2023 had trouble coupling at times. The warm pool back then was also less expansive than it is in recent times.

[Kingarabian]

Twin cyclones should develop in the SWPAC over the next 48 hours. Their winds are showing on the 850mb wind anomaly hovmollers.

[USTropics]

One aspect we have to think about is that the warm pool over the western Pacific has been prolific in the 2020s. The warm water expanse has been incredible El Nino or La Nina. 2023-2024 did not fully disperse this warm pool. It's physics, if the bathwater is continuously hot, any shift will allow it to move despite what ENSO was. This is something we don't fully understand with global oceans warming rapidly. A theoretical idea one could ask, since 2023-24 did not fully behave like a traditional Nino, could it be reason why we're seeing a more traditional one form so close?

1963-64, and then 1965-66 had a moderate and strong Nino pretty quickly.

So would you say the accumulation of subsurface warmth in the Indo-Pacific Warm Pool is a byproduct of the three consecutive Niñas i mentioned + general warming of the oceans? I think the latter reason in particular could explain why a triple dip Niña event like 1998-2001 didn't result in a strong/super Niño in 2002-03 (was moderate and CPAC-based iirc). Perhaps if it occured nowadays in a warmer oceanic climate it might have?

Something of that nature would be a thought. 1997 super El Nino was also very efficient in dispersing the WPAC warm pool both oceanic and atmospherically whereas 2023 had trouble coupling at times. The warm pool back then was also less expansive than it is in recent times.

This is a really good point. We are seeing a potential rapid-succession El Nino even because the 2023-2024 'recharge-discharge' was interrupted/muted. Like some of our previous discussions a few months ago, the previous El Nino was atypically forced (the background state was overwhelmingly warm), and the discharge phase was incomplete. While the thermocline flattened to a degree, the full volume of upper-ocean heat content wasn't able to fully evacuate.

It would be interesting to see if there is relative research on anthropogenic heat and how that impacts the WPWB (my assumptions are it has made it deeper and more voluminous). This would require a much stronger and prolonged divergence mechanism (like the wind stress/WWB we are seeing for oceanic transport). The 2023-24 El Nino event was definitely not fully coupled. Specifically, the Walker Circulation was decoupled (i.e., unusual easterly wind anomalies) and the global oceans (particularly the Atlantic) were uniformly hot (hence the ENSO teleconnections were muted).

Due to the inconsistent ocean-atmospheric coupling, the discharge event was sluggish. Heat was shifted more towards the CPAC, but didn't fully leave the basin. The lingering residual heat (especially at the subsurface) is one of the reasons we could be seeing a significant El Nino on the horizon. This research article does a good job of highlighting how the integrated OHC from 0 to 2000 meters has significantly increased in the past ~45 years. Essentially, the warm pool has anomalously gained heat from the eastern boundary current faster than it loses it to the northern boundary current.