A powerful Kelvin wave moving across the Pacific is headed for California, but it is not the dramatic wall of water some headlines suggest. According to The Verge, the wave is a slow sloshing of warm water along the equator that temporarily raises sea levels. This one is tied to a "super" El Niño, with eastern Pacific temperatures reaching 5 degrees Celsius above normal in early October.
The practical risk is that every extra inch of sea level can worsen flooding during storms and high tides. El Niño also tends to push storm tracks toward Southern California. The Verge notes California's governor declared a state of emergency in September, and coastal infrastructure already faces pressure from climate-driven sea level rise.
The warm water has mixed effects on marine life. It can bring tropical species north, as seen with a record striped marlin off Washington and hammerhead sightings in Southern California. But scientists are bracing for a potential die-off of kelp forests, which prefer cooler water, in an area already affected by a marine heatwave since May.