A high surf warning is posted for today through Wednesday as a new large northwest swell is expected to bring waves up to 20 to 30 feet on north shores of Oahu, Kauai County, Maui and Molokai.

West shores are expecting waves with faces of 12 to 20 feet.

The swell is expected to build today and peak Tuesday night into Wednesday morning. The warning is in effect until 6 p.m. Wednesday.

“Large breaking surf, significant shorebreak and dangerous currents make entering the water very hazardous,” the National Weather Service said.

Despite the high surf warning, waves at Ehukai Beach on the North shore were too small to hold the first round of the Billabong Pipe Masters surfing contest, organizers of the World Surf League competition said.

The latest swell follows a dangerous swell over the weekend and Monday that critically injured a surfer on Sunday and kept Oahu lifeguards busy Monday keeping people off the shoreline and off the rocks in places like Shark’s Cove on the North Shore.

“This surf is extremely dangerous and only the most experienced surfers with the correct equipment should venture out,” said Shayne Enright, a spokeswoman with the Ocean Safety Division of the Honolulu Emergency Services Department.

Lifeguards made four rescues Monday and issued 790 warnings or other preventative actions on north shores and conducted two rescues and issued 305 warnings and preventative actions on west shores, Enright said.

On Sunday at about 11:45 a.m., lifeguards at Ehukai Beach responded to a surfer unconscious in the water at the Banzai Pipeline.

The surfer, a 22-year-old man, caught a wave but didn’t resurface, Enright said.

A body surfer reached him and held on to him until lifeguards responded from shore.

He regained consciousness and paramedics took him to the hospital in critical condition.