Something enormous has been moving quietly up the Pacific toward Southern California.
Now, it’s here.
An El Niño-fueled coastally trapped Kelvin wave is arriving along the Southern California coastline, potentially raising background sea levels another 6 to 12 inches for weeks or even months. Unlike a normal swell, there’s no giant wave face approaching shore. It’s essentially an enormous, slow-moving bulge in the ocean hundreds of miles across.
“It is arriving now,” climate scientist Daniel Swain told the Los Angeles Times.
And its timing is concerning.
Southern California is already dealing with abnormally high ocean levels, severe beach erosion and repeated hurricane swells. In Santa Monica, water levels this week were running approximately 11 inches above NOAA’s predicted tides, according to the Times.
Ocean temperatures off Southern California are also roughly 7 to 8 degrees above average, with record warmth extending from central Baja into the region.
“It’s an important part of the development and evolution of El Niño,” explained Dr. Michael Jacox, a research oceanographer at the NOAA. “You can see the link from the tropical ocean all the way to the West Coast.”
Related: What Is a Kelvin Wave? And What Does It Mean for California Surf?
The Kelvin wave alone isn’t expected to suddenly inundate the coast.
“The Kelvin wave by itself will not cause flooding,” North Carolina State University scientist Dillon Amaya said. But combine that elevated baseline with high tides, storms and large swell, and the consequences can change dramatically.
That combination is already developing.
The National Weather Service has a Coastal Flood Advisory through Friday night for Malibu, Los Angeles County beaches, Ventura County beaches and Catalina and Santa Barbara islands. Forecasters expect minor to locally moderate flooding, dangerous rip currents and moderate beach erosion, particularly around high tide.
Hurricane Rachel’s southerly swell is arriving simultaneously, while additional west-to-northwest swell is expected behind it. The NWS says vulnerable areas include Malibu, Long Beach and Catalina, and warns that waves could wash people from beaches and rocks or capsize small boats near shore.
Related: Watch: Giant Rockslide Collapses Laguna Beach Cliff Amid Super El Niño Surf
The bigger concern may be what comes next.
Scientists expect at least two more significant Kelvin waves between November and January, precisely when California enters king-tide season and its greatest potential for winter storms. Swain said he is concerned coastal flooding could eventually resemble damaging El Niño winters such as 1982-83, 1997-98 and 2015-16.
NOAA explains that these waves begin when weakened equatorial trade winds allow warm, elevated water to shift eastward across the Pacific. Once reaching the Americas, that energy turns north and becomes trapped against the coastline.
For Southern Californians, the important part is simpler:
The ocean is already running high.
Now the baseline underneath the next big swell is getting higher.
Related: Hurricane Polo Is So Powerful People Are Asking About ‘Category 6’ (Video)
Original Post from this site