Somewhere beneath the Pacific Ocean, a vast pulse of warm water is on the move. It began near Indonesia and has been sliding east along the equator for months, a slow, invisible surge of heat that some scientists have described as stretching close to 14,500 km across the tropical Pacific.
No ship could feel it. No sailor could see it. Yet a Nasa satellite orbiting 1,300 kilometres overhead caught it in the act, because as the warm water passed, the ocean surface above it quietly rose by about 15 centimetres.
That gentle bulge, tracked through the spring of 2026, was the sea sending a warning months in advance. On June 11, the US weather agency National Oceanic and Atmospheric Administration (Noaa) declared that El Nino has formed, and forecasters believe it could grow into a rare and powerful event.
El Nino is the warm phase of a natural climate cycle in which the central and eastern Pacific heats up and reshuffles weather across the planet. Fishermen coined the name centuries ago. It is Spanish for the boy, a nod to baby Jesus, because the warming tended to peak around Christmas.
WHAT IS A KELVIN WAVE AND HOW DOES IT TRIGGER EL NINO?
Normally, trade winds blow across the Pacific from east to west, heaping warm water near Indonesia while cold, nutrient-rich water rises to the surface off Peru. This rising of deep cold water is called upwelling.
Every so often, the winds weaken and briefly reverse. The mountain of warm water in the west then comes sliding back east. This slow underwater surge, hundreds of kilometres wide and spanning much of the Pacific, is a Kelvin wave.
Because warm water expands and takes up more room, the sea surface above it rises. The wave also pushes down the thermocline, the boundary between warm surface water and the cold depths, which switches off the cooling upwelling near South America.
The eastern Pacific heats up, and El Nino is born.
HOW DID NASA’S SENTINEL-6 SATELLITE DETECT IT?
The Sentinel-6 Michael Freilich satellite, launched in 2020 by Nasa and its European partners, maps the height of the entire ocean every 10 days, accurate to fractions of an inch.
It spotted a small Kelvin wave near Micronesia in late January that faded by mid-February. A far larger wave emerged in early March and rolled east. By mid-May, the seas around Peru sat more than 15 centimetres above long-term averages.
WILL 2026 BRING A SUPER EL NINO?
Possibly. Noaa forecasters predict a 63 per cent chance that Pacific sea temperatures will breach 2 degrees Celsius above average, the mark of a very strong El Nino, like those of 1997 and 2015.
For India, that is an unwelcome guest. Strong events have historically weakened the southwest monsoon, though factors such as the Indian Ocean Dipole can soften the blow. The event should peak this winter. The ocean has spoken. The world now waits.
– Ends
