Off the west coast of Mexico, a mass of unusually warm water is creeping north. This wave will reach California and could bring the threat of coastal flooding, beach erosion, impacts to surfing and even potential damage to roadways by the water. 

More of these waves could follow, enhancing a potentially wetter winter for California due to the ongoing El Niño.

How it works

Now, this wave isn’t anything like a tsunami. It is a slow-moving wave, only moving north at about 6 mph, that you probably won’t even see.

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It is called a coastal trapped Kelvin wave, if you want the technical term.

El Niño is the culprit. It changes how the winds blow in the Pacific, allowing warm water to collect near South America. As water gathers, it can lead to a wave that moves along the shore and sets its sights on California, which we are seeing now.

(MORE: Everything El Niño)

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This wave should reach California by October, where it could raise sea levels by about a foot.

What it means for you

A foot of extra water might not seem like much, but that means more beach erosion and a higher risk of coastal flooding. Think of the beachgoers and the tourism that can be impacted by reduced beaches in these areas. Coastal inundation can also lead to damage to roadways and even potential sinkholes, which can cause travel delays.

And there is the matter of surfing in Southern California. You can see bigger waves, but reduced beaches mean a greater danger for newer surfers who are not used to having little room for error.

And then we have to talk about El Niño itself. El Niño winters can lead to wetter conditions for California. This is because the Pacific jet stream shifts south and brings rounds of storms through the southern tier of the country.

(MORE: The pineapple express is a firehose. El Niño just turned it up)

Powerful fall and winter storms can bring heavy low-elevation flooding, coastal flooding and beach erosion from gusty winds. Water levels raised by one of these waves will only make conditions worse. Also, should these factors come together during a King Tide, we could see serious problems.

El Niño can bring more of these waves, so this could even be the first of many. The last super El Niño in 2015 and 2016 brought more than one, so the water levels could rise again during storms too far out to reliably forecast.

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