Deadly 16-foot waves are expected to hit Northern California beaches, prompting officials to issue a “stay water” warning.
The National Weather Service (NWS) issued the alert on Tuesday, saying strong offshore winds will cause “hazardous swimming and surfing conditions and localized beach erosion.”
The weather advisory is in effect until 6 a.m. PT Wednesday for San Francisco beaches, northern and southern Monterey Bay, and Big Sur counties.
Deep water waves in the area are typically 10 feet high this month, but NWS meteorologist Dylan Flynn reported they could top 17 feet.
Even the most experienced swimmers have been warned to stay out of the water because large waves can create a strong undercurrent that will sweep people into the sea.
Those who visit northwest-facing beaches are most at risk of being swept underwater and are also advised to keep their pets away from the beach’s edge.
An atmospheric river that formed Sunday off the California coast was behind the high waves, but forecasters said it took 24 hours to reach shore.
Strong wind gusts could reach speeds of 50 to 60 miles per hour over the ocean, and although the wind will not reach the coast, the resulting waves still pose a major threat.
San Francisco beachgoers were warned to stay out of the water as 16-foot-high waves crashed into the shore.
‘Dangerous conditions for swimming and surfing and localized beach erosion. “Large waves can sweep across the beach without warning, sweeping people into the sea from rocks, piers and beaches,” the NWS said.
‘Sudden immersion in cold water can cause cold water shock even for the most experienced swimmers.
“Shock with cold water can cause dramatic changes in breathing, heart rate and blood pressure, greatly increasing the risk of drowning in open, turbulent water.”
The agency also noted that northwest-facing beaches are at high risk for large turbulent breakers and strong currents.
Although the NWS warning is in effect until Wednesday morning, Flynn said news week that another notice will probably be issued until Thursday.
The deep-water waves were caused by a storm-force low-pressure system that forms when low pressure associated with thunderstorms and hurricanes builds up in the atmosphere.
The low pressure at the center of the storm causes wind speeds to reach 60 kilometers per hour and forces air to rise into the atmosphere, significantly increasing the size and intensity of waves in the ocean.
Even the most experienced swimmers have been warned to stay out of the water because large waves can create a strong undercurrent that will sweep people into the sea (stock)
Deep-water waves only occur in ocean depths at least twice their wavelength, meaning that if the wave is 17 feet above the ocean surface, it formed where the ocean depth was greater than 34 feet.
When these waves approach the coast and enter shallow water, they can increase in height by 200 percent, a phenomenon known as shoaling.
This is where the wave’s energy becomes more concentrated as its speed decreases, causing the wavelength to shorten and its height to increase, causing larger breaking waves.
California has seen an increase in atmospheric rivers in recent years, with meteorologists reporting that the state was hit by nine in just three weeks, between December 2022 and January 2023.
Atmospheric rivers are relatively long, narrow regions that transport water vapor away from the tropics.
They can extend up to 1,000 miles in length, and consecutive atmospheric rivers, also called AR families, can cause significantly intense flooding.
“These start over warm waters, typically tropical oceans, and are guided toward the coast by low-level jet streams ahead of cold fronts of extratropical cyclones,” said Qian Cao, a hydrologist at the University of California, San Diego. PBS.
The first bout of heavy rain soaks the soil and prevents it from absorbing more liquid, causing water levels to build up and sea levels to rise.
This weather phenomenon typically occurs when large-scale weather patterns synchronize to form narrow stretches of intense moisture transport.
They can occur anywhere in the world, but occur primarily in mid-latitude regions, approximately 30 to 60 degrees north or south of the equator.