By Ann Duan
Seattle Times staff reporter
A giant pulse of warm water is surging toward the West Coast, and it’s expected to hit California in days, lifting sea levels by a half-foot or more and lingering for months.
Known as a Kelvin wave, it doesn’t present a severe threat to Washington yet, but the National Oceanic and Atmospheric Administration will be monitoring it with caution in October.
“If we see impacts in California, that’s our first heads up, a couple days later, it might come up here,” said Logan Howard, a meteorologist with the National Weather Service.
It’s nothing like a tsunami or a regular wave crashing on the beach. Instead, it moves slowly, deep underwater, hugging the coast.
“What happens is there are these slow, large temporary rises in sea level,” Howard said. “It moves up the coast like a wave.”
Kelvin waves are caused by changes in wind speed at the ocean surface along the equator, according to NOAA. They’re typically triggered by El Niño, and this is an El Niño year. That means surface waters are warming in the tropical Pacific.
Kelvin waves first hit California in May and June, according to NOAA, but this month’s wave is predicted to be much stronger.
California’s coastal communities have been bracing for rising sea levels, coastal flooding and erosion, which could impact homes, roads and access to power. Gov. Gavin Newsom declared a state of emergency in September to mobilize for El Niño impacts this fall and winter.
The wave’s damage could be compounded by climate change, which has already led to warmer waters and rising sea levels.
The pulse should weaken as it travels north, Howard said, but it’s still too early to rule out flooding and erosion on Washington’s coastline.
The wave’s impact will depend on atmospheric conditions around the time it reaches Washington, Howard said. For instance, low pressure and strong shore winds, pushing water up the coast, are signs that flooding and erosion could follow. Howard said experts are most concerned for Washington’s southern coast and along the Olympic Peninsula.
Washington could be in for a warm, dry winter with minimal snowpack, but nothing’s for certain. This year’s El Niño is expected to be “very strong,” but El Niño and La Niña are unpredictable.
“No two El Niño and La Niñas are the same,” Howard said.
Ann Duan: aduan@seattletimes.com. Ann Duan is a metro intern at The Seattle Times, covering a range of local news. She previously interned at The Daily Herald in Everett, The Olympian and U.S. News & World Report. She has also written for Street Sense Media and for The GW Hatchet while studying journalism at George Washington University. Duan grew up in Washington, between Renton, Mukilteo, Mill Creek and Shoreline.
