The National Weather Service has issued a High Surf Warning through at least 4 p.m. Friday for an expanse of the Northern California coast that includes San Francisco and other Bay Area counties, warning would-be beachgoers away for fear of dangerous waves.
National Weather Service (NWS), a division of the National Oceanic and Atmospheric Administration, says:
A High Surf Warning indicates that dangerous...battering waves will pound the shoreline. This will result in deadly rip currents. Remember, never turn your back to the ocean! [...]
Extreme wave run up is expected with these waves with long lulls in between wave sets, which will increase the risk of being washed into the sea by a wave. Expect large and dangerous surf.
NWS blames the unruly sea on “a strong storm system over the eastern Pacific” that will also make heavy, on-again, off-again rain likely through Sunday and has pushed some particularly dramatic, inky fog onto the bay Thursday morning.
When weather conditions make waves of more than ten feet likely, NWS will issue a High Surf Advisory to mark “a threat to life and property within the surf zone.”
A High Surf Warning, like the one in effect today, is more serious and indicates “especially heightened threat to life and property within the surf zone.”
In both cases the solution is to stay off the beach and away from the waterline if at all possible, and to be constantly watching for incoming waves if proximity to the ocean is for some reason unavoidable.
Hawaii Magazine notes “rushing forces of water are strong enough to pull someone just walking on the beach in the surf zone into and under the water.”
Every year beachgoers are swept out to sea in the Bay Area, usually with fatal results, including the case of a nine-year-old in Carmel in 2017. Even seemingly ordinary conditions may generate fatal waves.