Organizers of the Quiksilver in Memory of Eddie Aikau are cautiously optimistic that the big wave surfing competition will go Thursday — but the final call won’t be made until 6 a.m. Thursday.

So far, reports from buoys north of Hawaii show the swell is living up to computer projections of peak wave heights of 40 to 50 feet during the day on Thursday.

But contest officials will get a better idea of how big and clean the waves will be from buoy readings late tonight.

“There was a reason there was a saying the bay calls the day,” 1989/1990 Eddie winner Keone Downing said at a news conference today. “When we show up in the morning and we check our buoy reports … it gives us a real good idea. But until those solid, concrete pieces come in place, it’s always up in the air.”

The contest has only been held eight times since 1985 and is only held when waves are consistently clean and around 40 feet during daytime hours for at least six to eight hours. The last time the Eddie was a go was on Dec. 8, 2009.

Preparations for holding the contest are well underway with the construction of a grandstand and other facilities at Waimea Bay Beach Park.

State and city officials are preparing to handle the thousands of spectators expected to start descending on Waimea Bay late tonight. Special duty police officers, paid for by event sponsor Quiksilver, will deploy around Waimea Bay, to supplement police already on duty, Honolulu Mayor Kirk Caldwell said.

Honolulu police have plans for traffic to flow “as smoothly as possible,” even if surf runs over Kamehameha Highway, said Honolulu Police Department Major Kerry Inouye.

Police closed Kamehameha Highway from Laniakea to Turtle Bay to all but local traffic and The Bus during the high tide Monday afternoon, after surf from a giant swell rolled over the highway earlier in the day.

Inouye did not specify if police plans included closing the highway again Thursday morning.

Parking is restricted on Kamehameha Highway around Waimea Bay starting at 10 p.m. tonight, and spectators are encouraged to get there by walking, biking or taking the bus.

TheBus is adding additional buses along North Shore routes 52 (Honolulu-Mililani-Haleiwa) and route 55 (Honolulu-Kaneohe-Haleiwa) starting at 5 a.m.

The schedule is posted at TheBus.org website.

Heavy traffic is expected to slow the bus service and riders should allow for extra travel time.

Contest organizers will not be running private shuttles Thursday and spectators who park far away are encouraged to ride the bus.

The state and city are also canceling lane closures for utility and repair work on Kamehameha Highway and Kaukonahua Road along the North Shore on Thursday to help with traffic flow.

Some 15,000 to 18,000 people arrived at Waimea Bay on Feb. 10, before the big wave surf contest was canceled, event director Glen Moncata said.

Some of those spectators were able to park along Kamehameha Highway despite the parking restrictions — and many were ticketed and towed.

Barriers will make parking on the side of the highway difficult to impossible this time around, Honolulu Police Department Major Kerry Inouye said. That means that it will be more of a challenge for the thousands of spectators expected to arrive at Waimea Bay on Thursday than it was two weeks ago, he added.

City lifeguards will work longer hours watching the shores Thursday, from 7:30 a.m. to 6:30 p.m. to help keep spectators safe.

Event organizers noted that Aikau was a lifeguard and encouraged people to follow the advice of lifeguards.

Oahu’s North Shore and other areas on neighbor islands exposed to the northwest swell are under a high surf warning until 6 a.m. Friday.

Forecasters said the swell could runup over roads and cause coastal flooding, especially around the high tide, which is at 5:18 a.m. at Waimea Bay.

Bob Burke, a meteorologist with the Honolulu office of the National Weather Service, said people who are on or near the shoreline on the North Shore should be aware that the very large waves could sweep up the beach, even in areas that appear to be dry.

The event will also honor Haleiwa big-wave surfer Brock Little, who died of cancer on Feb. 18. Little, who rose to fame charging waves at the contest in 1986, was an alternate for this year’s competition despite his illness. A surfboard that Little rode in 1990 will be placed near a monument to Eddie Aikau at Waimea Bay, Moncata said.

People wishing to pay tribute to Aikau and Little are encouraged to bring a ti leaf.

If the contest is a go, it will be broadcast on the Internet on the World Surf League website and WSL mobile app. It will also be broadcast on the CBS Sports Network and on Oceanic Time Warner Cable channels 250 and 1250HD.

People planning to drive up to North Shore tonight should prepare for rain and cool temperatures. The forecast calls for scattered showers after midnight with low temperatures between 56 and 68 degrees and northeast winds around 10 to 15 mph.

Thursday should be sunny and breezy with some isolated showers in the morning, east winds of 15 to 20 mph and highs between 70 and 80 degrees.

The contest format features no eliminations.

Twenty-eight invited surfers will surf twice, in separate rounds in seven man heats. Surfers can ride up to four waves in each heat and the top four scores will be totaled to determine the winner. Anyone can win, even in the last round, if they ride a big scoring wave.

Judges will score each wave up to 100 points, based on size, risk and control.

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

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

If the Eddie is a go, it will be televised live on Oceanic SURF Channel with the morning show beginning at 7:30 a.m. and the competition set to begin at 8 a.m.