Surf of up to 35 feet is expected on the north shores of Oahu, Kauai, Niihau, Maui and Molokai this afternoon into Friday.
The National Weather Service has issued a high-surf warning that also includes the west shores of Kauai, Oahu and Molokai.
"Surf will remain elevated overnight then build rapidly Thursday, reaching warning levels on Kauai and Oahu by afternoon and Maui County in the early evening hours," the forecast said. "Large, hazardous surf will hold through Friday afternoon, then diminish."
The warning is in effect until 6 p.m. Friday, but advisory level surf is expected to continue until Sunday, when another swell arrives pushing surf up to dangerous levels again.
Surf is expected to be in the 10- to 15-foot range through this morning and build to 25- to 35-foot heights by this afternoon and evening on the north shores.
West-facing beaches will see 8- to 12-foot surf through this morning, building to 15 to 25 feet this afternoon and evening.
"This may be one of our largest and most dangerous periods of high surf this season," said Melvin Kaku, director for the Honolulu Department of Emergency Management. "We can expect sand and seawater incursion on roads and highways, and onto private property. We are also concerned that our homeless families living along affected coastlines could be at risk. We will be notifying service providers as well as tasking our Reserve Corps Volunteers to warn the homeless along those shorelines."
The most significant hazard to North Shore coastal areas can be expected to coincide with the high tide at 4 a.m. Friday. Residents living in homes along or near the shoreline should be prepared to evacuate immediately if their homes are threatened, city officials said.
A spokeswoman for the Quicksilver in Memory of Eddie Aikau big wave surfing competition said organizers are monitoring the two approaching swells to see if the contest, which is only held when waves are about 35 feet or higher, and consistent enough, at Waimea Bay, can be held.
She said, at this point, it looks like the waves may not be consistent enough to meet "Eddie" standards on Friday. But they are still looking at the swell that is expected to arrive Sunday.
The last time the contest was held was in 2009.
