The first in a series of northwest swells should bring waves of 15 to 20 feet today on north and west shores of Oahu, Kauai County and Molokai and west shores of Maui., according to the National Weather Service, which has issued a high surf advisory.
The advisory begins at 6 a.m. today through 6 p.m. Wednesday, but is likely to be extended through Thursday as another swell arrives.
West shores can expect 10- to 15-foot surf.
As the current swell lowers Wednesday, another northwest swell is expected to fill in Wednesday night and peak on Thursday close to high surf warning levels, forecasters said.
A third swell is expected to arrive Saturday.
Forecasters warn beach-goers can expect strong breaking waves, shorebreak, and strong longshore and rip currents making swimming difficult and dangerous.
People going to the beach should heed advice given by lifeguards and exercise caution, the National Weather Service said. Boaters should also expect recreational surfers utilizing harbor channels to reach surfing areas.