El Niño Flavors: Eastern Pacific, Central Pacific, and the Modoki Question

Line up the great El Niños of the satellite era and a family resemblance is obvious: warm water spreading across the equatorial Pacific, weakened trades, displaced rainfall. Look closer, though, and the family splits. Some events — 1982-83, 1997-98, 2015-16 — planted their warmest anomalies in the far eastern Pacific, hard against South America. Others — 2004-05, 2009-10 — parked their heat thousands of kilometers away, near the International Date Line, leaving the South American coast comparatively untouched. Same phenomenon, different address. And in a system where impacts follow the heat, the address matters.

Two archetypes

The first family is the Eastern Pacific (EP) event, also called the "canonical" or "cold tongue" El Niño because its warming overwrites the eastern Pacific's normally cool surface. These are the textbook events — the ones that flood coastal Peru, devastate the anchoveta fishery, and dominate historical accounts. The monsters of the modern record are all EP events.

The second family is the Central Pacific (CP) event, with maximum warming near the Date Line while the far east stays near normal. It goes by several names — "dateline El Niño," "warm pool El Niño" — but the most memorable label came from Japan: El Niño Modoki, coined by Toshio Yamagata's research group in 2004. Modoki is Japanese for "similar but different," and it is hard to imagine a more apt scientific name. A Modoki event looks like an El Niño, walks like an El Niño — but its center of action, and therefore its consequences, are shifted.

Why location changes everything

Recall from our teleconnections explainer that El Niño's global reach comes from displaced tropical rainfall: deep convection follows the warmest water, and the atmosphere downstream responds to where that heat engine sits. Move the heat engine 4,000 kilometers west and you move the source of the planetary waves that reshape the jet streams — so the pattern of remote impacts shifts too.

The local differences are the most intuitive. In an EP event, warm water directly bathes the South American coast, and coastal Ecuador and northern Peru face sharply elevated flood risk. A CP event may largely spare them, because the eastern Pacific never warms enough to move the rain there. Remote impacts differ as well, though less cleanly — and here forecasters add an important caveat: stronger events, which tend to be eastern-leaning, deliver "more reliable impacts over the globe," as NOAA's ENSO Blog puts it. Weak CP events give the atmosphere a quieter, more ambiguous push, so their teleconnections are noisier.

Strength and flavor travel together

That correlation between strength and flavor appears to be systematic, not coincidental. NOAA's ENSO Blog summarizes it directly: "Weaker El Niños tend to be closer to the Central Pacific types and stronger El Niños tend to be closer to Eastern Pacific types." A modeling study spanning 4,000 years of simulated climate reinforced the link, finding that the farther east an event's warming peaks, the stronger the event tends to be.

The physics is plausible enough: the eastern Pacific is where the thermocline is shallowest and the ocean-atmosphere feedbacks bite hardest, so an event that manages to ignite warming there has access to the full Bjerknes amplifier described in how El Niño develops. Central-Pacific warming, sitting over a deeper thermocline, has less leverage.

A continuum, not two boxes

It is tempting to sort every event into an EP or CP bin, and early research often did. The field has since pulled back. As the NOAA ENSO Blog emphasizes, there are "more than just the two" types — events fall along a continuum of peak locations, spatial patterns, and amplitudes, and a single event can even migrate, beginning with one distribution of warmth and ending with another. The EP/CP vocabulary is best treated the way sommeliers treat tasting notes: a useful description of tendencies, not a rigid taxonomy.

This is the same lesson that emerges from the definitional disputes among agencies: ENSO resists clean categories. Thresholds and types are human conveniences draped over continuous natural variability.

The climate-change wildcard

One reason flavor research matters beyond taxonomy: the mix may be changing. More CP events have been observed in recent decades, a shift noted in the IPCC's Sixth Assessment Report — but whether that reflects greenhouse warming, natural decadal variability, or simply the limits of a short observational record remains unresolved. Models disagree about how event diversity should respond to a warming ocean, just as they disagree about future ENSO amplitude more broadly (see ENSO and climate change).

For now, the practical takeaway is this: when the next El Niño headline arrives, ask not just "how strong?" but "where?" An event's flavor — eastern, central, or somewhere along the spectrum — is one of the best early clues to which coastlines should brace and which may be quietly spared. Precise definitions of the terms used here live in the glossary.