Deadly 15-foot waves are expected to hit Northern California beaches, prompting officials to issue a “stay water” warning.
The National Weather Service (NWS) released the warning on Tuesday, saying strong, strong offshore winds will cause “dangerous swimming and surfing conditions and localized beach erosion.”
The weather advisory is in effect until 6 a.m. PT Wednesday for beaches in San Francisco, 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 be as high as 15 feet.
Even the most experienced swimmers have been warned to stay out of the water as the large waves can create a strong undertow that will pull people into the sea.
Those visiting northwest-facing beaches are at greatest risk of being pulled underwater and are also advised to keep their pets away from the beach shore.
An atmospheric river that formed off the coast of California on Sunday was behind the high waves, but meteorologists said it took 24 hours for them to reach shore.
The strong gusts can reach speeds of 80 to 90 kilometers per hour over the ocean and although the winds do 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 waves crashed against the shore
‘Dangerous swimming and surfing conditions and local beach erosion. Large waves can crash over the beach without warning, pulling people into the sea from rocks, jetties and beaches,” the NWS said.
‘Sudden immersion in cold water can result in cold water shock for even the most experienced swimmers.
‘Cold water shock can result in dramatic changes in breathing, heart rate and blood pressure, significantly increasing the risk of drowning in rough open water.’
The agency also noted that northwest-facing beaches are at high risk of large turbulent coastal breaks and strong currents.
Although the NWS warning is in effect until Wednesday morning, Flynn said Newsweek that new advice 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 in the atmosphere.
The low pressure at the center of the storm causes winds to reach 60 kilometers per hour and forces the 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 as the large waves can create a strong undertow that will pull people into the sea (stock)
Deep water waves only occur at ocean depths at least twice their wavelength, meaning that if the wave is 5 meters above the ocean surface, it forms where the ocean depth was greater than 10 meters.
When these waves approach the coastline 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 its wavelength to shorten and its height to increase, leading to larger breaking waves.
California has experienced an increase in the number of 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 and narrow areas that transport water vapor outside the tropics.
They can extend up to 1,000 miles (1,600 kilometers) in length, and successive atmospheric rivers, known as AR families, can cause significant heavy flooding.
“These start over warm waters, typically tropical oceans, and are guided toward the coast by low-level jet streams ahead of the cold fronts of extratropical cyclones,” Qian Cao, a hydrologist at the University of California, San Diego, told me. PBS.
The first heavy rain soaks the soil and prevents the soil 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 and form narrow stretches of intense moisture transport.
They can occur anywhere in the world, but are most common in mid-latitudes – about 30 to 60 degrees north or south of the equator.