A monster 75ft wave has been recorded off California after a so-called “bomb cyclone” pounded the US West Coast.
It is the tallest documented by scientists at the University of California during the last 15 years a monitoring project has run.
Over that time, the average tallest wave height has not been more than 10ft in winter.
But during the recent weather phenomenon, where hurricane-strength winds saw gusts of more than 100mph, the average height of the tallest waves was 45ft with the largest measuring 75ft.
They were recorded about 20 miles off the coast of Cape Mendocino in northern California
The storm that impacted the California coast last week generated some of the largest waves ever recorded by CDIP buoys. At Cape Mendocino, CDIP staton 094, the significant wave height was 13m/43ft and the largest wave measured was 22.7m/74.4ft!https://t.co/FeUStWsF9A
— CDIP Buoys (@CDIPBuoys) December 2, 2019
A bomb cyclone is effectively a rapidly intensifying storm caused by a sharp drop in air pressure, which in turn generates strong winds.
The recent storm brought with it rain and snow and set low-pressure records in northern California and parts of Oregon, according to forecasters.
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James Behrens of San Diego’s Coastal Data Information Program said the height of the waves recorded was “definitely unusual” for the time of year.
“These kinds of really large waves are usually only detected way out in the middle of the ocean, when winds are being generated,” he told CNN.
The project’s monitoring buoys had only measured taller waves at one other station, located in the remote North Pacific Ocean, where extreme waves are expected to form on occasion, he said.
Troy Nicolini, head of the weather service at the National Oceanic and Atmospheric Administration (NOAA), said the bomb cyclone had caused a so-called dynamic fetch, when strong winds move in the same direction and speed as the waves it is generating.
Fortunately, the unseasonably large waves came ashore during low tide which reduced their impact.
Mr Nicolini said: “It’s often just a game of chance.
“If they came at a peak time, they would’ve caused significant damage.”