The Wave You Won’t See Coming: Why California Is Watching the Pacific

By Cliff Potts | WPS News BAYBAY CITY, Philippines — October 1, 2026, 21:05 PHST

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A Kelvin wave is not a tsunami. It is not a storm surge, and it is not a giant surface wave rolling toward California.

It is a large-scale movement of water through the ocean that can raise coastal sea levels as it travels. You could be standing on a California beach while one passes and never see anything resembling a conventional wave.

But the ocean level can change.

That distinction is important because California is watching a coastally trapped Kelvin wave associated with the developing 2026–27 El Niño. By itself, the phenomenon is not necessarily disastrous. The concern is what happens when elevated coastal water combines with high tides, large surf, erosion and Pacific storms.

A Wave Thousands of Miles Long

During El Niño, winds that normally blow westward along the equatorial Pacific weaken and can periodically reverse. Those changes can generate oceanic Kelvin waves that travel eastward across the Pacific.

After reaching Central and South America, some of that energy can continue northward along North America as coastally trapped Kelvin waves.

NOAA describes this as an “oceanic teleconnection” between the tropics and the U.S. West Coast. These disturbances travel primarily through the ocean but can raise coastal sea levels by approximately 15 centimeters — roughly six inches — measurable by satellites and tide gauges (National Oceanic and Atmospheric Administration [NOAA], 2026a).

That does not sound particularly frightening.

By itself, it isn’t.

The Problem Is What Goes on Top

Think of the Kelvin wave as raising the floor.

Put an unusually high tide on top of that elevated starting point.

Then add large Pacific surf or storm surge.

Then perhaps an atmospheric river dumping heavy rain onto already saturated ground.

The Kelvin wave does not have to create the disaster. It can change the conditions under which another event occurs.

That is why California officials are paying attention.

On September 21, Gov. Gavin Newsom proclaimed a state of emergency as California prepared for what officials say could become a historically strong El Niño. The proclamation directs state agencies to prepare vulnerable communities and infrastructure and stage flood-control and emergency-response equipment ahead of possible flooding, landslides, debris flows and coastal hazards (Office of Governor Gavin Newsom, 2026b).

The governor’s announcement also noted that California had already experienced coastal flooding associated with El Niño conditions as Kelvin waves elevated sea levels while offshore storms generated strong surf (Office of Governor Gavin Newsom, 2026b).

The Kelvin wave is therefore not the entire story. It is one ingredient in a much larger developing weather and ocean system.

California Is Already Starting From Behind

This also isn’t happening to a pristine coastline.

California has already dealt with coastal flooding and erosion this year. Beaches, bluffs, roads and other infrastructure that have already taken punishment can become more vulnerable when another round arrives.

Meanwhile, NOAA reported September 25 that the developing El Niño was expected to strengthen through the Northern Hemisphere winter. Its California Current assessment said additional warming along the coast was expected as El Niño-forced Kelvin waves arrived (NOAA, 2026b).

That doesn’t guarantee catastrophic weather.

El Niño changes probabilities and underlying conditions. It does not tell us precisely where the next storm will hit, when it will arrive or how severe it will become.

That distinction matters.

So What Should Californians Actually Do?

If you own a cabin in the Appalachians and have always dreamed of mountain living, this article isn’t going to discourage you.

But coastal Californians do not need to sell the house because a Kelvin wave is coming.

They should determine whether their home, workplace and regular travel routes are vulnerable to coastal or other flooding. They should know where they would go if authorities order an evacuation. They should also pay closer attention when high tides, coastal-flood advisories, high-surf warnings and major storms begin overlapping.

Someone living well inland or high above the coastline faces a very different risk from someone living beside a low-lying beach, harbor, river mouth or coastal road.

That makes local information particularly important. Californians should follow National Weather Service forecasts and warnings along with instructions from county and municipal emergency-management agencies.

California’s official preparedness guidance emphasizes knowing your flood risk, receiving emergency alerts, planning evacuation routes and avoiding flooded roadways (Office of Governor Gavin Newsom, 2026a).

California Preparedness Checklist

• Know whether your home and workplace are in areas vulnerable to flooding.

• Sign up for local emergency alerts.

• Know at least two evacuation routes when practical.

• Keep medications, drinking water, flashlights, batteries, chargers and essential documents accessible.

• Include pets and anyone needing assistance in your evacuation plan.

• Watch local weather, tide, high-surf and coastal-flood forecasts.

• Never drive through floodwater.

• If local authorities issue an evacuation order, leave.

The important word is local.

California has more than 800 miles of coastline, and conditions can vary enormously. A warning that matters greatly to a low-lying coastal neighborhood may have little direct relevance to someone living miles inland.

Preparation should match the actual risk.

What Californians Should Take Away From This

The larger lesson is that natural disasters do not always arrive as isolated events.

We tend to give them individual names: earthquake, wildfire, flood, hurricane, atmospheric river.

Reality can be messier.

Serious damage can occur because several individually manageable conditions happen at approximately the same time.

That is the useful way to understand California’s Kelvin-wave problem.

The Kelvin wave can elevate the baseline coastal water level. A high tide can raise it further. A Pacific storm can produce storm surge and large surf. Heavy rainfall can simultaneously create inland flooding and destabilize hillsides and coastal bluffs.

None of those ingredients guarantees catastrophe.

Put enough of them together, however, and something that normally would have been manageable can become substantially more dangerous.

That is why residents near vulnerable portions of the coastline should not focus exclusively on the Kelvin wave itself. They should watch what develops around it.

When authorities close a beach, pier, coastal road or bluff area, take the closure seriously. Don’t go down to the shoreline simply to watch the weather. Don’t assume that because a particular road has survived previous storms it will remain passable during the next one.

And don’t treat uncertainty as evidence that nothing will happen.

Nobody can say today exactly how the pieces will come together during the coming El Niño season. Some communities may experience relatively little. Others could find themselves dealing with the wrong combination of tide, surf, rainfall and geography.

That uncertainty is precisely why preparation matters.

California isn’t preparing for some enormous invisible wave suddenly smashing into Los Angeles.

It is preparing for what happens after the Pacific quietly raises the starting line.

For coastal Californians, that is the takeaway worth remembering:

The Kelvin wave probably won’t be the disaster. Those extra inches of ocean could make the next disaster worse.

And if all else fails, yes, there are always the Appalachians.

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APA-Style Sources

National Oceanic and Atmospheric Administration. (2026a, September 3). Ocean indicators we’re tracking for El Niño’s arrival on the West Coast. NOAA Fisheries.

National Oceanic and Atmospheric Administration. (2026b, September 25). California-Current Ocean Assessment Status Takeaways (C-COAST): 2026–27 El Niño and marine heatwave updates. California Current Integrated Ecosystem Assessment.

Office of Governor Gavin Newsom. (2026a, September 14). Ready is how California leads, and every Californian has a role to play. State of California.

Office of Governor Gavin Newsom. (2026b, September 21). Governor Newsom proclaims state of emergency to bolster statewide El Niño preparedness, protect California. State of California.