King tides broke records along the Southern California coast this week, and forecasters say the next round, due Thanksgiving week, could push the water even higher. On Oct. 27, the tide gauge at San Pedro in Los Angeles Harbor reached about 8.18 feet, the highest since record keeping began there in 1923. Newport Beach hit 8.4 feet, and seawater shut down Pacific Coast Highway in Huntington Beach. There was no hurricane and no major storm. The ocean just came up.
The cause is El Niño. A slow surge of warm tropical water called a Kelvin wave, combined with ocean temperatures several degrees above normal, has lifted the sea along parts of Southern California by roughly a foot to a foot and a half. Ordinary high tides are now arriving on a raised floor.
What are king tides and why were these so high?
King tides are the highest tides of the year. They happen when the moon, sun and Earth line up, with an extra boost because Earth sits closer to the sun late in the year. They are predictable. What changed in October was the baseline. Off Los Angeles, the ocean was near 72 degrees around Halloween, about 7 degrees warmer than usual, according to KMPH meteorologist Kris Kuyper. Warm water expands, and that expansion alone can add around half a foot. The Kelvin wave adds about another half foot. Stack a normal 6.5 foot October tide on top of that, and you get an 8 foot tide rolling into the streets.
Where did the king tides flood?
Water poured across PCH between Seal Beach and Huntington Beach, closing the highway in both directions at times. On the Balboa Peninsula in Newport Beach, neighbors sandbagged homes that had stayed dry for decades. Gauges in La Jolla and Santa Barbara also set preliminary records.
Florida went through its own version that same week. Virginia Key, near Miami, logged a record 10 straight days of moderate flooding, with water levels topped only by hurricanes Irma and Wilma.
Will Thanksgiving king tides be worse?
Probably. Oceanographer Greg Dusek told weather.com that California’s Thanksgiving week tides should run about half a foot higher than October’s. He said that means significant flooding is likely even if El Niño does not lift the ocean any further. More king tides follow around Christmas and again in late January. If a storm or strong onshore winds line up with any of those windows, the flooding gets worse…