Surf generated by Hurricane Iselle and a higher-than-normal tide could create a dangerous storm surge, weather and civil defense officials said.
Surf along east shores is expected to reach 8 to 15 feet through Friday. South shores are in the 1 to 3 foot range Thursday, rising to 5 to 8 feet Friday.
Surf is expected to increase rapidly late Thursday and peak early Friday, with damaging surf possible before diminishing slightly Saturday, forecasters said.
Hurricane Julio may bring more surf to the islands this weekend.
“Extremely rough surf conditions are expected to accompany the passage of Iselle near the vicinity of Oahu overnight Thursday into Friday,” forecasters said.
The surf coincides with a high tide of about 2 feet or higher in the afternoons.
“The high surf and hight tide combination will bring the potential for coastal flooding along low-lying areas,” forecasters said.
“Overnight Thursday has potential for tropical storm conditions making for chaotic breakers with a mix of wave periods from 6-15 seconds. Even with the lower tides overnight Thursday into the morning, coastal surf-induced impact is expected to become significant,” the National Weather Service surf forecast said.