The MJO doesn't cause El Niño. But without it, most strong El Niños would never reach their full strength. Here's the mechanism, the history, and what it means for 2026 right now.
If you've read the MJO explainer, you know the basics: a 30–60 day pulse of enhanced tropical rainfall circling the globe, tracked by its RMM phase and amplitude. When it reaches the western Pacific in phases 5–7, it can fire off westerly wind bursts that kick Kelvin waves eastward. That's where the basic explainer stops.
This page goes one level deeper — into how that kick becomes a year-long Pacific warming, why the relationship runs both ways, and what it means that the 2026 El Niño is already strong while the MJO is currently sitting in phase 1, temporarily quiet.
The connection between the MJO and El Niño runs through a specific sequence. Each step takes weeks. Together they span months.
One wind burst rarely makes an El Niño. The MJO's real power is that it arrives in repeated pulses every 30–60 days, each potentially launching another Kelvin wave. Research finds that the MJO accounts for 60–70% of the equatorial thermocline variance — the signal that most directly tells forecasters how much warm water is being stored and shifted. When successive Kelvin waves arrive in step and constructively interfere, the warming accelerates. When they arrive out of phase — or when easterly wind bursts intervene — the event can stall.
The relationship doesn't run only from MJO to El Niño. It also runs the other way — and that feedback is part of what makes a developing event like 2026 self-accelerating.
Under neutral or La Niña conditions, the MJO's convective pulse tends to weaken and dissipate as it moves eastward past the Maritime Continent, because it encounters cooler ocean water in the central Pacific. Under El Niño conditions, the warm pool extends east, so MJO convection can propagate farther into the central Pacific — and the wind bursts that come with it push deeper into the same waters that are already warming. NOAA's own June 2026 language describes this: as the "low-frequency base state" (the El Niño itself) strengthens, passing MJO pulses "constructively interfere" with it and amplify the westerly signal.
"The MJO is not the fuel. The warm subsurface reservoir is the fuel. The MJO is the spark — and a developing El Niño makes the spark easier to ignite."
This two-way coupling also creates one of the core challenges in El Niño forecasting. Because the MJO is semi-random in its timing, a strong subsurface heat reservoir doesn't guarantee a strong surface El Niño — it depends on whether the right MJO pulses arrive at the right time. This is a primary driver of the "spring predictability barrier": El Niño forecasts issued before July are inherently less reliable because they can't know yet whether the MJO will cooperate.
As of late June 2026, the El Niño is officially present and strengthening — but the MJO is temporarily in a quiet phase.
The MJO's current quiet patch doesn't mean it's done helping. A moderate-to-strong MJO pulse passed through the western Pacific in early June and — as BOM's June 16 Tropical Climate Update noted — likely intensified the westerly trade-wind anomalies during El Niño's development. That pulse has now moved into the Western Hemisphere, where it's weakening. But models expect it to re-emerge and amplify over the western Pacific in early-to-mid July, potentially delivering fresh westerly forcing at a critical moment.
NOAA's CPC has flagged the key open question explicitly: "the strongest El Niño events in the historical record are characterized by significant ocean-atmosphere coupling through the summer, and it remains to be seen whether this occurs in 2026." The MJO behavior over July–September is the single biggest swing factor for how strong this event ultimately becomes.
The July 9 CPC ENSO Diagnostic Discussion — the next major scheduled update — will be the first place this summer's MJO-ENSO coupling gets assessed against actual data. Watch both the MJO phase and the freshness of subsurface Kelvin-wave activity when it publishes.
It's worth being honest about one thing the research still debates: how much of the 1997-98 and 2015-16 events was driven by the MJO specifically, versus the broader seasonal wind pattern and the Pacific/North Pacific Meridional Mode (PMM/NPMM). A 2025 Science Advances study argued the North Pacific Meridional Mode has a larger impact on El Niño evolution than the March MJO specifically. The honest answer is that these forces overlap and interact — the MJO is an important, well-documented contributor to El Niño onset and intensification, not the sole cause. The warm subsurface reservoir, the seasonal wind pattern, and the background state of the Pacific all matter.
The MJO is the most watchable near-real-time signal available — it updates daily, it's publicly tracked, and its connection to the Kelvin-wave mechanism is well-established. That's what makes it a useful lens for following how this event develops week by week.
Track the current RMM phase and amplitude on the MJO Assist panel on the dashboard. For the full phase diagram and forecast model output, see NOAA CPC MJO Update and BOM MJO Monitoring. This page will be updated following each July CPC ENSO Diagnostic Discussion.
NOAA CPC ENSO Diagnostic Discussion, June 11, 2026 · BOM Tropical Climate Update, June 16, 2026 · IRI ENSO Quick Look, June 2026 · McPhaden, "Genesis and Evolution of the 1997-98 El Niño," Science, 1999 · Hu & Fedorov, PNAS, 2016 (2014 easterly burst) · Hu & Fedorov, Climate Dynamics, 2017 (2015-16 wind bursts) · Zavala-Garay et al., Journal of Climate, 2005 (MJO stochastic forcing) · NOAA PSL MJO Primer