Environment & Science

Full moon, El Niño could produce 7-foot Christmas Day swells in SoCal

Surfer Jono Hall of Newport Beach gets ready to body surf big waves at a spot known as the Wedge.
Surfer Jono Hall of Newport Beach gets ready to body surf big waves at a spot known as the Wedge.
Benjamin Brayfield/KPCC

Listen to story

00:53
Download this story 0MB

A coastal flood advisory is in effect for the Los Angeles area until Friday morning due to a phenomenon known as king tides.

These occur when the sun and moon align in a way that creates maximum pull on the Earth’s waters.

In fact, on Christmas Day there will be a full moon amping up these tides. The last time that happened was in 1977, and the next one will be in 2034.

But that’s not the only factor raising ocean waters this winter, said Bob Guza, a professor at the Scripps Institution of Oceanography. Like with so many other weather phenomenon, El Niño is playing a role.

Guza said the El Niño pattern is warming water in the Pacific Ocean causing the water to expand.

"It doesn’t expand much," he noted. "But the ocean is way deep, so, if you get 1 percent expansion, that’s significant."

Guza added that El Niño is also changing global wind patterns, so that more is blowing toward the California coast. All of this has led to a roughly 6-inch increase in the mean water level of the ocean.

Combine that with already powerful king tides, and forecasters say L.A. may see high tides this week peak at around 7 feet above low ones.

Stuart Seto with the National Weather Service says these high tides will arrive in the morning hours, and people near the beach should take heed.

"Harbor walkways, campgrounds, anything that's right around the beach will be affected by these king tides," Seto said.

The flood advisory is set to end Friday December 25th at 10 am.