Surfer hurt in wipeout at Mavericks as waves hit 50 feet

A surfer takes off on a large wave at Maverick's in Half Moon Bay, CA Wednesday, January 7, 2016. A surfer takes off on a large wave at Maverick's in Half Moon Bay, CA Wednesday, January 7, 2016. Photo: Michael Short, Special To The Chronicle Buy photo Photo: Michael Short, Special To The Chronicle Image 1 of / 72 Caption Close Surfer hurt in wipeout at Mavericks as waves hit 50 feet 1 / 72 Back to Gallery

A surfer underwent emergency surgery after wiping out Thursday on one of series of giant swells reported at Mavericks, the famed big-wave surfing spot off Half Moon Bay.

Garrett “GMAC” McNamara, 48, was recovering Friday from surgery on his arm and shoulder after he bit the raging surf during a practice session for the upcoming Maverick’s competition.

McNamara’s wipeout was caught on video and showed him catching a giant wave before falling off his board and tumbling down the face of the breaker. He was quickly scooped up by rescuers and brought to shore.

The National Weather Service issued a high-surf advisory for most of the Northern California coastline Thursday that extended into Friday morning. Westerly swells were averaging 13 to 16 feet, the weather service reported.

“Extreme wave run up is expected with these waves with long lulls in between wave set ... increasing the risk of being washed into the sea by a wave,” the weather service said in its statement.

On Thursday, surfers reported waves up of to 50 feet at Mavericks. Organizers of the annual big-wave surfing contest declared that a “potential swell is on the horizon,” the first stage in the alert process that eventually will summon two dozen of the world’s best surfer dudes to drop everything and head to Half Moon Bay. But a go-date for the contest was still pending.

Last year, the waves never got big enough and the contest was canceled. But from the looks of Thursday’s wave action, this year’s event promises to be a doozy.

Bill Hutchinson is a San Francisco Chronicle staff writer. E-mail: bhutchinson@sfchronicle.com Twitter: @bill_hutchinson