The National Weather Service [NWS] has issued a high-surf advisory for the entire Bay Area, from Point Reyes National Seashore to the Big Sur Coast, where large and potentially dangerous waves could pose a significant danger at the beach all day Wednesday and into Thursday morning.
The NWS forecast notes that “a large, long-period northwest swell has arrived at the coastal waters and will persist through Thursday morning,” possibly spawning “seas of 15 to 17 feet, with breaking waves to 22 feet in the surf zone.”
Furthermore, the advisory warns:
Beach visitors, surfers, fisherman and others visiting the beaches should be prepared for rapidly building seas with dangerous crashing waves in the surf zone. Sea surface temperatures in the mid 50s will cause hypothermia in a short amount of time.
The surf zone has been relatively tranquil and this will be a quick change in surf conditions. Beach and water related fatalities are common but preventable. Dont become a statistic. [...] High surf will affect beaches in the advisory area, producing rip currents, localized beach erosion, and sneaker waves.
#120718SR1 UPDATE We are saddened to announce that despite all efforts made by community members (bystander CPR) and the Rescue crews, that the victim has succumbed to his injuries. Our thoughts and support are with his family and friends https://t.co/pFHxUFGAEG— SAN FRANCISCO FIRE DEPARTMENT (@SFFDPIO) December 8, 2018
The warning is in effect from now until 9 a.m. Thursday.
This type of warning is fairly common along the coast, with similar conditions manifesting a few times each year.
However, that does not mean that the advisory should be treated casually. Residents in affected areas should avoid beaches if possible and exercise extreme caution if a trip to the ocean is unavoidable. Never turn your back on the ocean.
In 2019, NWS recorded 68 drowning deaths from rip currents and similar hazards in the U.S. during advisory periods, including three in California. So far in 2019 there have been 17 in the country, two of them in the state.
Although NWS did not record any Ocean Beach deaths during high-surf advisories in the past 15-plus months, fatalities have occurred there even under normal conditions.
In December, the San Francisco Fire Department rescued 43-year-old Oakland resident Jay Seideman from waters near the SF Zoo. He later died at the hospital.
The advisory also warns of hypothermia risk from water temperatures. According to the University of Minnesota, approximately 600 people in the U.S. die from hypothermia every year, a condition that occurs when exposure to cold temperatures lowers the body’s temperature to dangerous levels.
“Cold water dangerously accelerates the onset and progression of hypothermia, since body heat can be lost 25 times faster in cold water than in cold air,” warn university researchers.