The National Weather Service extended a high surf warning through Thursday night because of a new giant swell arriving today that could bring more 50-foot waves to north shores of Oahu and other islands.

No major problems were reported Tuesday from the current declining swell. However, Oahu lifeguards reported 24 rescues on the North Shore, 22 of them at Waimea Bay. The fire department said there were no calls overnight for surf-related damage.

The high surf warning for north- and west-facing shores of Kauai County; and the north-facing shores of Oahu, Maui and the Molokai is now in effect until 6 a.m. Friday.

Surf on the north shores of most islands declined Tuesday to still-giant levels of 30 to 40 feet from the nearly 55-foot sets seen Monday. North shores of the Big Island were expecting wave faces of 20 to 30 feet. The west-facing shores of Oahu and Molokai saw 18- to 25-foot surf.

Forecasters said the current swell should briefly drop below advisory levels today, however wave heights will rise rapidly tonight as a new giant swell arrives and peaks on Thursday.

North shore wave heights will lower to 12 to 18 feet today, then rise rapidly tonight to heights of 40 to 50 feet. West shores of Oahu and Molokai should see wave heights decline to 8 to 12 feet today before rising to 20 to 25 feet late tonight. North shores of the Big Island should expect surf to decline to 10 to 15 feet today, before rising again to 20 to 25 feet Thursday.

A spokeswoman for the Ocean Safety Division said surfing conditions improved as the swell dropped, allowing surfers to catch some of the giant swell on the North Shore.

Lifeguards reported a number of broken boards and leashes. Lifeguards on rescue watercraft rescued 20 surfers from the surf at Waimea and two bodyboarders from the shore break. Two other people were rescued at other North Shore beaches and lifeguards issued 1,180 warnings to beachgoers.

West shore lifeguards did not report any rescues, but issued 600 preventative actions.

Haleiwa Beach Park, Alii Beach Park and Waimea Bay Beach Park reopened Tuesday morning after no major problems were reported Tuesday morning, following wave run-up that flooded parking areas Monday. However, the restrooms at Waimea remain closed while city crews worked to empty a septic tank.

Keawaula Bay, also known as Yokohama Bay, in the Kaena Point State Park remained closed Tuesday because of high surf.

On the Big Island, Old Government Beach Road in Waa Waa briefly reopened before the county closed it again because of surf Tuesday afternoon. The county also closed Laaloa, Kahaluu, Mahukona (wharf side) and Kekaha Kai (Kua Bay section) beach parks Tuesday.

The world’s best big wave surfers were notified Tuesday that the Quiksilver in Memory of Eddie Aikau big wave surf contest is on a green alert because of the upcoming swell. A decision on whether to run the event will be made Thursday morning, if the surf shows up as expected.

Organizers said however, there is a concern that the surf could be too big and dangerous to hold the competition.

Waves from the new swell could be even larger than the choppy, 55-foot surf that hit the North Shore on Monday.

If the Eddie is not a go, another giant swell is forecast to arrive starting Sunday or Monday and peaking Tuesday.

But the holding period for the Eddie lasts only until Monday, so that swell could arrive one day too late to hold the contest.