Above, local California station has coverage of one way in which El Niño will exert strong effects on the state, including Coastal Flooding, which is already underway.
It’s called a Coastaly Trapped Kelvin Wave, and the physics behind it are fascinating.
If you’re interested, Daniel Swain had a really great discussion of this in his super valuable “Office Hours” YouTube session a few weeks ago, which I’ve excerpted here. The full length session is at this link, and worth your time.
Here’s the Kelvin wave explainer, about 10 minutes. Get coffee.
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.
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.
This wave should reach California by October, where it could raise sea levels by about a foot.
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 sinkholes on roads, 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.
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.
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Swain is interviewed for this local LA CBS report: