2026 ENSO Updates

[cycloneye]

Webb has the scope of how things are progressing with ENSO and at the end, it comes down to how strong the upcomming El Niño may be.

 https://x.com/webberweather/status/1994809836115300611



 https://x.com/webberweather/status/1994814570649849932

[Kingarabian]

We should have a pretty stout warm pool moving east soon to open up the new year. GFS continues to show a WWB over the WPAC. Need to see if the trades near the dateline begin to slow down during January.

[cycloneye]

The weekly CPC update of 12/1/25 has niño 3.4 up from -0.8C to now -0.6C.

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

[Dean_175]

Another "semi" La Nina (at least under current climatology)? I once again don't see how 5 trimonthlies will be reached, just like last year. I think it will probably get 4 (ASO, SON, OND, NDJ), but DJF may struggle to make it- possibly falling just shy of the required -0.5C,particularly if this event decays as quickly as some models are showing. Probably will be upgraded to an official La Nina in a future warmer climatology though. I consider it to be one, but maybe for now, 2024 and 2025 will go down as unofficial La Nina events that produced La Nina conditions without reaching the currently official definition that is based only on ONI.

[Dean_175]

Sorry for the double post, but I have a question: in light of the post on the 2025 thread about WWB event in the eastern Indian Ocean on top of -IOD, I started to wonder: how effective really is the heat transport between the Indian Ocean and west Pacific? Indonesia is in the way. Equatorial Kelvin waves can partially go around barriers as some of the energy is converted to coastal Kelvin waves that then comes back together into an equatorial one on the other side, with some of the signal instead reflected as a Rossby wave depending on the poleward extent. I have known this from my equatorial dynamics course. However, looking at the geography of the area, it appears that it would be hard for warmth to travel east in this manner around Indonesia and southeast Asia. There is a land barrier between north Indonesia/Papua New Guinea and southeast Asia with few gaps, so I imagine it would be hard for much energy to travel through that way. Malaysia forms a land bridge to the rest of SE asia that would seem to block it fairly effectively.To the south, it is a bit more open, but still filled with narrow gaps. Does anyone have an estimate on how leaky the Indonesian boundary actually is to ocean transport from the equatorial Indian ocean? This is relevant for west Pacific ocean heat content going into the new year, which is a leading indicator of ENSO and high OHC early on seems to possibly be a requirement for a strong to very strong El Nino event.

[USTropics]

Sorry for the double post, but I have a question: in light of the post on the 2025 thread about WWB event in the eastern Indian Ocean on top of -IOD, I started to wonder: how effective really is the heat transport between the Indian Ocean and west Pacific? Indonesia is in the way. Equatorial Kelvin waves can partially go around barriers as some of the energy is converted to coastal Kelvin waves that then comes back together into an equatorial one on the other side, with some of the signal instead reflected as a Rossby wave depending on the poleward extent. I have known this from my equatorial dynamics course. However, looking at the geography of the area, it appears that it would be hard for warmth to travel east in this manner around Indonesia and southeast Asia. There is a land barrier between north Indonesia/Papua New Guinea and southeast Asia with few gaps, so I imagine it would be hard for much energy to travel through that way. Malaysia forms a land bridge to the rest of SE asia that would seem to block it fairly effectively.To the south, it is a bit more open, but still filled with narrow gaps. Does anyone have an estimate on how leaky the Indonesian boundary actually is to ocean transport from the equatorial Indian ocean? This is relevant for west Pacific ocean heat content going into the new year, which is a leading indicator of ENSO and high OHC early on seems to possibly be a requirement for a strong to very strong El Nino event.

Perfect time for me to apply what I've been learning in my oceanography class. To answer your first question, we have the Indonesian Throughflow (ITF) current, where the water transport is actually Pacific -> Indian (not the other way around). This is analogous to the Caribbean transport of water/salinity into the GOM via the Gulf Stream:


If you're interested more in this, I would recommend this research article that explores this in more detail. The main takeways are if we wanted to quantify this, we would use Sverdrup (Sv). From the article, there is about a 10-15 Sv net volume transport from the Pacific into the Indian Ocean through Makassar (see image above). In terms of Sv transport, this is rather minor (for instance, Gulf Stream is ~30 Sv through GOM and Florida Straights and around 150 Sv near Newfoundland).

Kelvin wave interaction is definitely interesting and not well researched. I would imagine when we have westerly wind bursts that propagate along the equator, and then turn along Sumatra/Java, this modulates the ITF transport on intraseasonal timescales (30-90 days). So dynamically, the system is definitely not 'sealed' like you stated (i.e., Kelvin waves do affect sea level and currents).

So to conclude all this, Sv transport is rather small (I would classify it as a second-order effect) but not a non-negligible effect that impacts WPAC OHC.

[cycloneye]

Euro has transition to El Niño by next summer.

 https://x.com/AndyHazelton/status/1996925878232617458



 https://x.com/AndyHazelton/status/1996926395306615103