The Kelvin wave 2026 phenomenon is drawing attention as a large pulse of warm ocean energy moves across the Pacific during a strengthening El Niño. Unlike ordinary waves that break along a beach, this type of Kelvin wave operates on a planetary scale and can change ocean levels along coastlines.
Scientists are watching the event because the additional rise in coastal sea levels could coincide with high tides, winter storms and storm surge. Current research indicates that the effects may be particularly important along California and other parts of the U.S. West Coast during the fall and winter of 2026–27.
Latest Update: September 29, 2026
As of September 29, 2026, the Pacific is experiencing a strengthening El Niño, and scientists are monitoring coastally trapped Kelvin waves that are expected to affect the U.S. West Coast. NOAA’s California Current assessment, updated September 25, says additional warming along the coast is likely in the coming weeks because of El Niño-forced Kelvin waves.
NOAA’s September 10 ENSO discussion said there was greater than a 90% chance of a very strong El Niño during the Northern Hemisphere fall and winter of 2026–27. The agency also said there was a 75% chance that the October–December period would produce an event exceeding the strength of previous El Niños in the historical record dating to 1950.
Recent reporting indicates that the Kelvin wave moving toward California could temporarily raise coastal sea levels by roughly 6 to 12 inches in some locations. The precise local effect will depend on the wave, tides, winds, storms and coastline characteristics.
What Is a Kelvin Wave?
A Kelvin wave is a large-scale ocean wave that can travel along the equator and later become trapped against a coastline. It is very different from the waves people see breaking on beaches. It is better understood as a moving pulse or signal in ocean height and temperature.
Warm Kelvin waves are closely associated with El Niño. They develop when the normal east-to-west trade winds in the tropical Pacific weaken or temporarily reverse. When that happens, warm water that has accumulated in the western Pacific can move eastward.
NASA’s satellite observations during 2026 detected several warm Kelvin waves. A small wave formed around Micronesia in late January, while another developed in early March and moved eastward. By mid-May, sea levels near Peru were more than 15 centimeters above their long-term averages.
How the 2026 Kelvin Wave Developed
The 2026 event is connected to a major change in Pacific Ocean conditions. During a normal period, trade winds help keep warm surface water piled up in the western tropical Pacific. When those winds weaken, the balance changes and warm water can begin moving east.
The resulting Kelvin wave travels beneath and along the ocean surface. It can carry a large amount of ocean energy across thousands of miles without producing a visible wave at the beach.
NASA explains that several Kelvin waves can appear over a number of months before and during the development of El Niño. As warm water accumulates in the eastern Pacific, the ocean and atmosphere interact in ways that help strengthen the climate pattern.
Why the Kelvin Wave Is Heading Toward California
When an equatorial Kelvin wave reaches the eastern Pacific and encounters the coastline of South America, part of its energy can become a coastally trapped wave. Instead of continuing directly east, the signal can travel north and south along the coast.
Scientists are particularly interested in what happens when that signal moves north along the Pacific coast toward Mexico, California and the rest of the western United States.
NOAA Fisheries has been monitoring this process because coastally trapped Kelvin waves are one of the ocean indicators associated with El Niño’s arrival along the West Coast. Scientists are comparing current conditions with earlier strong El Niño events, including 1997–98.
How Much Could Sea Levels Rise?
Current scientific and media reports generally place the potential temporary increase along parts of California at several inches, with estimates reaching approximately 6 to 12 inches. ABC7 reported that scientists expect the Kelvin wave to raise sea levels by as much as a foot in some areas.
This does not mean every California beach or coastal community will experience exactly a one-foot increase. Ocean levels vary from one location to another, and local conditions can amplify or reduce the effect.
The Kelvin wave also does not mean that a giant wall of water will suddenly arrive on the shoreline. Scientists describe it as an elevated background ocean state. That elevated baseline can become important when another event, such as a storm or unusually high tide, pushes water levels even higher.
Why High Tides Could Make the Situation Worse
One of the main concerns is the combination of a Kelvin wave with high astronomical tides. If the ocean is already several inches higher than normal and a high tide occurs at the same time, coastal areas begin with less room before water reaches roads, beaches, drainage systems and buildings.
Storm surge can add another layer. A strong storm pushes seawater toward the coast, while large waves can send additional water onto beaches and coastal infrastructure. A higher background sea level means the same storm can potentially cause more flooding than it would under lower ocean conditions.
This is why scientists are not describing the Kelvin wave by itself as a catastrophic event. Instead, the concern comes from the interaction between elevated ocean levels,
