El Niño-Driven Kelvin Wave Approaches California, Elevating Seas This Fall

A coastally trapped Kelvin wave born of El Niño is steadily moving up the Pacific and is set to reach California this fall, with San Diego due by late September, Los Angeles soon after, and San Francisco by mid-to-late October. The wave will raise sea levels by about 4–8 inches and warm coastal waters (mid-80s F off Baja; near 70 F near San Francisco), fueling a marine heatwave and increased erosion. While not a tsunami, the higher baseline tides will heighten flood risk during peak high tides and full/new moons, and El Niño could bring more winter rainfall, shaping coastal conditions and ecological impacts through the season.