A heat wave that drives you to the shore, warm water temperature that draws you to the surf and a yellow flag “for moderate rip currents” that hints at danger, but doesn’t prevent you from swimming: These conditions can prove to be a dangerous, even deadly combination, according to research by the National Weather Service.
Most people know that rip currents, caused by breaks in the sandbar, can make swimming dangerous and require numerous lifeguard rescues during the summer.
But the National Weather Service, over the winter and spring, analyzed a number of other factors and found it is a mix of conditions that can lead to a drowning death where rip currents are a factor.
What they found was there are days when the risk of dying from rip currents in South Jersey are greater than others. It comes down to factors such as water temperature, time of day and how hot it is in Philadelphia. They are broken down into behavioral, measurable risk and demographic indicators.
“It’s what entices us to go in the water,” said Lance Franck, meteorologist for the National Weather Service in Mount Holly.
And why was Philadelphia chosen? Because it’s the largest city in NWS Mount Holly's coverage area and far enough from the ocean that it’s not subject to cooling sea breezes.
When it gets hot in the City of Brotherly Love, people flock to the beach.
But whether they’re at the beach or not, swimmers also prefer warm water. On average, the water temperature in Atlantic City is above 60 degrees from June 1 to Oct. 15, when most people are on the beach. Water temperatures above average may further entice people to hop on in.
Between 1998 and the end of September 2017, there were 47 rip current fatalities in the NWS Mount Holly’s coverage area, which includes the Atlantic coastal counties of Monmouth, Ocean, Atlantic and Cape May in New Jersey, as well as Sussex County in Delaware. Of those 47, 24 deaths were in Ocean (11), Atlantic (6) and Cape May (7) counties; 2017 was the deadliest year since the NWS began counting, with eight people dying.
Franck said those incidents were the only ones they could clearly attribute to rip currents.
“There could be more,” he said.
According to the study, the most common times for rip current fatalities are when air temperatures in Philadelphia are more than 3.1 degrees above average as well as when water temperatures are above 60 degrees (with a temperature anomaly of 2.5 degrees in Atlantic City, which was used as the focal point for the research).
Finally, when the rip current risk is moderate, as opposed, to high, they found the highest amount of rip current fatalities.
That may or may not be surprising, but as Franck pointed out, fewer people actually are swimming when the risk of rip currents are high — and the flags are red.
However, for a moderate risk of rip currents, associated with a yellow flag, shore beach patrols, “may have swimming restrictions, but may not also,” Franck said.
Randy Townsend, lifeguard captain for Harvey Cedars, backs up that assessment, although he believes most risks can be avoided if swimmers heed lifeguard warnings.
“The general public ... are very aware of the risks associated with these circumstances. However, you do have individuals who do not pay attention to the warnings and often wind up in a life-threatening situation,” he said.
The NWS research found other factors, including wave heights, the interval at which the waves pass, and wind direction are all factors.
Among their finds, rip currents presented the greatest threat when:
Waves were at least 2 feet high.
Wave intervals measured at the buoys, was 8 seconds or slower.
Winds were perpendicular to the land.
Franck said that the longer the wave period, “the greater the impact, because the waves have more strength to them.”
In addition, tropical systems, even if they are hundreds of miles away, can lead to longer periods swells and additional periods, which will also raise the rip current risk, Franck noted.
The data show swimming at a guarded beach is, in fact, the best way to avoid being overwhelmed by a rip current.
“The majority of fatalities occur at unguarded beaches,” Franck said.
A male (85 percent) between the ages of 12 to 34 (68 percent) had the highest risk factor. In addition, 62 percent of deaths were between 5 p.m. and 9 p.m., which is after hours for many beach patrols.
Townsend said Harvey Cedars has taken these factors into account.
“Our agency has an after-hours program every day of the 11-week (third week in June to Labor Day Weekend) summer season. We have mobile units on patrol from 5 p.m. to 8 p.m. to assist the public with whatever they may need.”
To help beach patrols, the NWS this year began holding conference calls with lifeguard chiefs and captains up and down the Jersey Shore and on Delaware beaches.
This ‘boots on the ground’ method of listening and sharing ideas holds promise to save even more lives. Townsend said having direct access to the National Weather Service and its information is exciting news.