A slow-moving wave is travelling up the North American coast and is expected to raise water levels in the Bay Area by nearly a foot in October. But it’s not going to be one giant crashing wave; in fact, people may not even notice it if they head to the coast.
The swell moving up the coast is a planetary-scale process, meaning it’s thousands of miles wide, known as a Kelvin wave, and is a direct impact of El Niño. During an El Niño event, winds shift and draw warmer ocean water from offshore and push it towards Central America. When the warmer water slams into the coast, it sends a coastally trapped wave, also known as a Kelvin wave, up the West Coast and towards Alaska, which can take months at a time.
But again, it won’t be one giant wave that you can see crashing at the beach. The wave is currently moving north across Central America’s coast at around 6 mph. It’s expected to arrive to Baja in the next week or so, Southern California by late September/early October, and the Bay Area by the first or second week of October.
Multiple Kelvin waves
These waves can bring elevated sea levels for weeks at a time, eventually subsiding before the next wave hits. Yes, there will likely be several Kelvin waves this season. The last big El Niño in 2015-2016 featured five to six Kelvin waves, which at times coincided with atmospheric rivers that led to record high wave heights across the state…