Ask Lookout: Why are beach hazards more frequent and dangerous in winter?

When winter rolls in, the ocean unleashes its wild side. High surf, rip currents and sneaker waves become more common, making beach hazard alerts almost routine. But what’s behind this seasonal phenomenon?

Calm waters can suddenly turn perilous in these cooler months, creating a recipe for danger. Beach hazard statements, high surf advisories and high surf warnings, from least to most threatening, are the official National Weather Service alerts notifying Santa Cruz County residents of these risky conditions. They range from moderate dangers to waves so large and unpredictable that even seasoned beachgoers are advised to stay out of the water.

One of the biggest threats is the unexpected sneaker wave, which can sweep much farther up the beach than anticipated. Gary Griggs, a professor of earth and planetary science at UC Santa Cruz, explained that at the Santa Cruz Wharf, waves come from various sources: storms in the North Pacific Ocean, tropical swells from Hawaii and local wind-driven swells. These waves all move at different speeds and heights. When two wave fronts align, their crests combine to produce a much taller wave. This is known as constructive interference. And it’s not a matter of if it will happen, but when these powerful waves will appear on any given day.

Rip currents — silent, powerful and deadly — pose another significant hazard at Santa Cruz County beaches. They form when waves push water up the beach, which then funnels back to the ocean through narrow channels, sometimes shaped by underwater sandbars or rock formations that direct the flow of water. These currents are often identifiable by a break in the waves, marked by discoloration or a brownish tint from the sand it’s taking with it.

“What goes up must come down,” said Brian Garcia, a local surfer and warning coordination meteorologist in the National Weather Service’s Monterey office. Just like gravity pulls a ball back to the ground, water pushed up the shore has to find its way back to the ocean, taking the easiest path through gaps in the seabed and forming a rip current.

These currents can pull swimmers out to sea with surprising force. “Water is literally the most powerful and lazy thing I’ve ever experienced. And I say lazy because it’s always going to find the path of least resistance. It’s powerful because there’s no fighting it,” said Garcia.

To make the ocean a triple threat, longshore currents join the party, moving water and sediment down the beach, carving out the narrow channels that aid in rip current formation. Beaches like Seabright State Beach in Santa Cruz, tucked behind coastal points, are especially vulnerable because waves often break at an angle, cranking up the intensity of those longshore currents. Throw in a sneaker wave dumping more water onto the shore, and you’ve got a dangerous combination intensifying both the longshore and rip currents.

All three hazards are interconnected, and they’re more frequent in winter, as North Pacific storms send larger, longer-period swells our way, turning the ocean into a force to be reckoned with. Many longtime Santa Cruz County residents might think they’re used to the rhythms of the sea here, but experts warn that those patterns are shifting.

“We’re going to have waves here forever, but they’re going to change. They’re not the same as they were when your dad was surfing here. Bottom conditions change, wave climate changes,” Griggs said.

Borja Gonzalez Reguero, UC Santa Cruz associate professor and researcher of coastal science and policy, agrees. He said that as the climate continues to change, shifting storm patterns in the North Pacific could bring more extreme wave events to our shores, with waves coming from different directions or with longer periods than previously. While average conditions might not change drastically, the shift in weather patterns could make peak surf more hazardous. To better understand the potential impact on Santa Cruz County’s coast, Reguero and his colleagues are developing wave climate data to explore local wave variation and its causes.

With these rising risks, Garcia said it’s crucial for beachgoers to stay vigilant, especially in the winter months: Keep a safe distance from the water, take time to observe the waves, get to know the tides, and look for the highest wet-sand mark to gauge where the waves have been. When in doubt, ask someone who knows the water well, like a lifeguard or a local surfer.

The alerts we receive on our phones should be taken seriously, said Garcia: “If I see someone with a soft-top board and their wetsuit on backwards, trying to surf on a big day, I tell them, ‘It’s not your day. Live to see another day.’”

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