What-makes-sneaker-waves-so-sneaky-and-dangerous

Blogs.kqed.org published this very worthy reading article recently with an interesting title: What-makes-sneaker-waves-so-sneaky-and-dangerous by Craig Miller of KQED Science. Some important point that everyone should aware:

These waves are especially sneaky because they can often occur when the weather is perfectly nice.

“We don’t see a lot of weather during these events,” says Larry Smith, a meteorologist at the National Weather Service in Monterey. “And that kind of feeds into the ‘sneaker wave’ thing.”

But the presence of sneaker waves means that the weather is bad somewhere. . . 

That's not reassuring, but pretty much summed it up what it is all about! Here's more:

. . . while size matters, a sneaker’s danger is compounded by the speed it’s moving when it hits the shore.

“A lot of times these waves may only be 4-6 feet in the open sea,” says Smith. “But they’re moving at a much higher velocity than we usually see on the coast.” Meteorologists measure the velocity of a moving wave by the “period,” the distance from the bottom of the trough on one side of the wave to the bottom of the trough on the other side.

Smith and his colleague, Warren Blier, got their pencils out for us and calculated that in open waters, where the wave is seeing little-to-no friction, a 5-foot-high wave with a period of 20 seconds will be traveling at a highway speed of around 70 mph, easily twice as fast as the more typical waves we see along the coast. It’s not uncommon for sneaker waves to have periods of 20 seconds or more.

“When the waves begin to feel the beach bottom they will begin to slow down substantially,” says Smith. So that wave with the 20-second period will hit a typical beach at something like the speed of a running adult.

Unfortunately, many of our beaches aren’t typical. “The catch is that along our coast we have many steep beaches that don’t slow the fast-moving wave down,” says Smith, citing as examples Monastery and Carmel River Beaches, located just south of Carmel.

Since there's no systematic scientific research done on these feaque waves publicly available yet, and indeed all beaches are not typical, the local practical experiences from coast guards and weather forecasters are most certainly invaluable and should always paid attention to!  Beach goings are for enjoyments, nearshore freaque waves are part of the nature's offerings, be on guard! Don't let these unexpected yet expected happenings ruin our well deserved enjoyments!