A high surf warning is in effect until 6 a.m. Friday for the north and west shores of Niihau, Kauai, Oahu and Molokai, the north shore of Maui and the west shores of the Big Island of Hawaii.
The National Weather Service predicts "giant" waves with 40 to 50 foot faces for north shores, with west shore waves possibly reaching 20 to 30 feet. West shores of the Big Island may have waves of 12 to 18 feet.
The wave heights may rival those that hit Hawaii on Jan. 28, 1998, a day some have nicknamed "Big Wednesday."
Waves are forecast to rise rapidly before midnight for Niihau and Kauai, by sunrise Wednesday for Oahu, around mid-morning for Molokai and Maui and Wednesday afternoon for the Big Island. Surf is expected to remain at warning levels through Thursday night.
Forecasters said the high surf and dangerous currents will make it extremely hazardous to approach the shoreline and result in significant injury or death. Significant coastal inundation and property damage is also possible, so road closures may be likely. Large breaking waves may also make it impossible to enter or leave harbors, including Kahului Harbor on Maui and Waianae Boat Harbor on Oahu.