El Niño continues to gain strength in the Pacific Ocean and will not peak for a few more months. Yet, it is already jaw-dropping. Temperatures are 5 or more degrees Celsius above normal and will get hotter. That’s greater than 9 degees Fahrenheit if you don’t think in Celsius. While I will avoid using adjectives like “super” or "Godzilla," I certainly understand why some people are using them. It will be an unprecedented event with significant impacts across the globe. This week, I started seeing stories and imagery of massive waves crashing into California. I knew it was time for a proper discussion of Kelvin waves, their relationship to El Niño, and potential impacts to the U.S. West Coast.

“During El Niño, winds that typically blow westward along the Equator weaken and periodically reverse in “westerly wind bursts.” These wind bursts set off oceanic Kelvin waves that travel east along the Equator,” according to a blog on the NOAA Fisheries website. “After reaching Central and South America, the waves travel north as “coastal trapped waves” along the North American coast,” The website went on to say. While their impact is already detectable along the U.S. West Coast, fall and winter will bring greater impacts according to research scientist Nate Mantua, who is based at NOAA’s Southwest Fisheries Science Center in Santa Cruz, California.

Satellites started tracking the Kelvin wave moving across the Pacific Ocean this spring. “Sea level height data from the international Sentinel-6 Michael Freilich satellite collected from March to May 2026 show higher, warmer water moving from the western Pacific Ocean to just off the coast of Colombia, Ecuador, and Peru,” according to a NASA website . One of the satellites used is Sentinel-6 Michael Freilich, which happens to honor a long-time NASA scientist and former colleague of mine. By May, the satellite data showed that seas were nearly 6 inches higher than average near Peru because water expands in response to warming.

The additional heat also changes circulation patterns and rainfall patterns in the region and globally, which is evident in satellite-based precipitation analyses shared in an email by Robert Adler of the University of Maryland. The warming caused a shift in something called the Walker Circulation, which affects how the main rainfall systems are distributed. A key message is how connected sea surface temperatures, sea surface height, precipitation, and Kelvin waves are to each other.

Potential Misrepresentation Of Kelvin Wave Impacts

My colleague Michelle L’Heureux wrote an excellent piece in 2015 asking if Kelvin waves could become the ocean version of the Polar Vortex. A media “buzzword” that is poorly explained and misunderstood. “The waves that most of us are familiar with are the waves at the beach—waves that endlessly curl and crash on the shore,” She wrote. Kelvin waves are a class of larger-scale atmospheric and oceanic planetary waves. "Unlike the waves you see at the beach, Kelvin waves do not curl over and then crash. They are more like the waves in your bathtub, which slowly slosh around. They don’t break, but they still have broad peaks and valleys that change the depth of the water (the ocean equivalent is “sea surface height”), L’Heureux explained.

I have already seen misleading portrayals of massive waves, but the impact of the Kelvin waves will be seen in different waves. “A few inches of extra ocean may not sound like much, but coastal flooding is a game of margins stacked on margins,” wrote Sean Macaday in The Sacramento Bee . “The wave itself will not flood anything on its own — this is not a tsunami, and there will be no moment when it “hits.” Instead, it quietly raises the baseline the tides ride on top of for weeks or months at a time,” he cautioned. That’s responsible reporting right there and likely Macaday sensing the same sensationalization potential that we often see with the Polar Vortex.

Effects On Water Temperature and Fisheries

“As these Kelvin waves move north along the coast, they deepen the thermocline—an underwater boundary at which temperatures drop rapidly at greater depths,” The NOAA blog continued. El Niño also causes changes in atmospheric pressure patterns over the northern Pacific. These “teleconnections” can affect wind patterns that force deep, cold water packed with nutrients to move upward. That can lead to warmer waters near the shore from southern California to Alaska. Warmer waters have less nutrients than the colder water from deeper levels, so that can affect fisheries in the region. However, some migratory species that like warm water can also appear.

“These species—such as dorado, striped marlin, and yellowfin tuna—have already extended their ranges north along the West Coast as marine heatwaves have warmed coastal waters without El Niño,” said NOAA. “An extended warm period from 2014 to 2018 began with a large marine heatwave known as The Blob and concluded with El Niño,” NOAA experts said. During those years, scientists found the presence of 36 unusual species off California including giant manta ray, blue marlin, whitenose shark, and wahoo.