Waves as high as 20 to 30 feet are expected to pound the north shores of most islands today. The west shores will also get their fair share of 12- to 20-foot surf.

A high surf warning is in effect through 6 p.m. for north and west shores of Kauai, Molokai, Niihau and Oahu, the National Weather Service said. Maui’s north shore is also under a high surf warning.

The Billabong Pipe Invitational surf contest is underway at Ehukai Beach Park with conditions described as “massive.”

Thirty-two surfers are competing for two wildcard slots in the upcoming Billabong Pipe Masters competition.

Surf was about 10 to 15 feet this morning, organizers said.

“It’s really clean out there,” said World Surf League Commissioner Kieren Perrow, in a news release.

The competition was postponed for a day as the big swell did not arrive as expected Tuesday.

Wave faces Tuesday were about 6 to 10 feet on Oahu’s North Shore and 6 to 9 feet on Kauai’s north shore.

Still, Ocean Safety lifeguards issued 395 warnings and made 16 rescues on the North Shore and 370 warnings and six rescues in West Oahu.

Beachgoers should beware very strong breaking waves and strong longshore and rip currents, the Weather Service said. Breaking waves might also hit harbors, making navigating harbor channels dangerous.

“Large breaking surf, significant shorebreak and dangerous currents make entering the water ver hazardous,” forecasters said. “Beachgoers, swimmers and surfers should heed all advice given by ocean safety officials and exercise caution.”

The northwest swell is expected to gradually decline through the week.

A new advisory-level swell is expected next week.