Record-setting 75-foot-tall wave recorded off California coast

[TexasTowelie]

A 75-foot-tall wave was recorded less than 20 miles off the California coast last month, and scientists at UC San Diego's Scripps Institute for Oceanography say it's the largest individual wave ever recorded by their network of coastal buoys.

While waves this size are common in the open ocean, this one recorded at the Cape Mendocino buoy (No. 94) on the evening of Nov. 26 was unusually close to California's Lost Coast.

"Waves of that size usually only occur far out at sea where the wind has been blowing across a big area," said James Behrens, the principal development engineer and manager for Scripp's Coastal Data Information Program. "The only other station in the network that measured a wave this large is deployed 800 miles off the coast of Washington."

The buoys also measure average wave height every 30 minutes. This wave fell within a period when the average was about 43 feet tall, the largest average ever recorded by Scripps coastal buoys. The typical average at this buoy in winter is 10 feet.

Read more: https://www.sfgate.com/weather/article/75-foot-tall-wave-largest-ever-California-14893034.php

[PJMcK]

1. Thankfully, almost all large waves crest before landfall

Think of an ocean wave like a sine wave: the 75-foot measurement is the difference between the crest (top) and the trough (bottom) of the wave. Accordingly, to the neutral observer, the actual height of the wave is 1/2 that distance.

In fluid dynamics, the wave needs the trough to balance the crest. If the depth of the water will not sustain the trough, the crest will break. As the wave approaches land, and the depth of the water decreases and the wave will usually be unsustainable and will break.

However, when at sea, a boat will experience the full 75-foot wave as it passes beneath the boat. Oddly, if the crests are not breaking, the boat will be relatively safe as it rides up and down the waves. Of course, it takes a great deal of wind to produce a wave of that size and that's a whole different set of physics that will impact the boat!

[2naSalit]

2. Thankfully....nt