As ocean swells associated with the remnants of Hurricane Arthur dissipated Sunday, an official cautioned that rip currents like those that followed the storm were likely to recur before summer’s end.
The National Weather Service issued a one-day warning that dangerous rip currents were possible at area beaches Sunday, but Bill Simpson, a meteorologist at the service’s Taunton office, said the powerful currents can be a danger at any time.
“There are just so many variables,” he said. “People should always be careful.”
Subtle but deadly, a rip current is a narrow, swift channel of water flowing away from a beach, often shaped by sandbars, jetties, or other obstructions, according to the National Oceanic and Atmospheric Administration.
Rip currents do not only precede or follow storms, like those bracketing the July Fourth holiday, but also can accompany many kinds of wind shifts, he said. Westport’s Horseneck Beach always has rip currents, Simpson said, because it gets strong southwestern winds. And while rip currents are more likely at south-facing beaches, they are also common on the Outer Cape from Wellfleet to Eastham, he said.
Such currents, Simpson said, are visible as disturbances in the flow of waves; they can appear as areas of choppy water and may have a different color than waves surrounding them.
Such variations can be hard to discern from the beach, where unsuspecting bathers can be lured into danger.
In May 2011, a 12-year-old girl from Lawrence died after being caught in a rip current at Hampton Beach, N.H. Two men from Massachusetts drowned after about a dozen swimmers were caught in a rip current at that beach in July 2005. One year later, a 55-year-old man drowned in a rip current off Nantucket’s Madaket Beach.
The weather service recommends swimming at beaches with lifeguards, never swimming alone, and avoiding piers and jetties where permanent rip currents can exist. A swimmer caught in a rip current should remain calm and attempt to swim parallel to the shoreline until out of the current, then swim at an angle away from the current and toward shore.
Dawn Leaks, director of communications for the American Red Cross of Massachusetts, said a recent Red Cross survey showed that more than half of Americans think they are stronger swimmers than they are.
“People have a sense of false confidence when it comes to the water,” she said.
Leaks said beach-goers should designate someone to watch any children near the water, swimmers should use the buddy system, and weaker swimmers should wear Coast Guard-approved life jackets. Swimmers also need to be mindful of water conditions, she said.
“People often don’t realize that swimming in the ocean is different from swimming in a pool,” she said. “So it’s really important for people to prepare themselves for the environment they’re going to be swimming in.”
Simpson said the tug of a rip current can be subtle, so that a person does not feel the pull until he or she has traveled several yards.
One of the greatest dangers, Simpson said, lies in nearby swimmers attempting a rescue rather than summoning a lifeguard. “A lot of people end up drowning when they try to help someone in danger,” he said. “The outgoing swimmer trying to save someone, they can get pulled down by the struggling swimmer.”Globe correspondent Todd Feathers contributed to this report. Jeremy C. Fox can be reached at email@example.com. Follow him on Twitter @jeremycfox.