Kelvin Wave In Pacific Ocean Heads Toward California

A mass of unusually warm Pacific water, called a Kelvin wave, is heading for the California coast and is expected to reach San Francisco in about three weeks. It's being driven by a strong El Niño, which has calmed the winds that normally push warm water toward Australia and Asia. Instead, that warm water is sloshing back toward the Americas, piling up along the West Coast.

For homeowners near the coast, this matters because the warm water is expected to raise sea levels there by 6 to 12 inches, on top of the roughly 8 inches oceans have already risen over the past century. Scientists also expect more rain and stronger winter storms in Southern California as a result. The bigger risk comes when storms line up with unusually high tides, which forecasters expect around Thanksgiving and Christmas — that combination is what tends to cause the worst flooding and coastal erosion. Governor Gavin Newsom has already declared a state of emergency, and the state is positioning road-closure equipment and preparing National Guard search-and-rescue teams for possible flooding.

Kelvin waves themselves are a natural, recurring ocean phenomenon, but researchers say this year's El Niño could be the strongest in 1,000 years, which makes the effects harder to predict and potentially more severe. If you live in a low-lying coastal area of California, it's worth keeping an eye on local flood warnings and storm forecasts through the winter and into early next year, since this pattern is expected to linger.