Another round of king tides will hit Friday and Saturday

Hawaii will experience another round of exceptional king tides Friday and Saturday as some of the highest tides of the year will again be enhanced by higher-­than-normal sea levels.

Phil Thompson, associate director of the University of Hawaii Sea Level Center, said the islands will likely experience the same kind of coastal erosion, wave overwash and temporary flooding in low-lying areas and around storm drain systems seen in late May and late April.

However, flooding impacts could be worse if high surf and/or heavy rain occur at the same time, Thompson said.

That is a possibility. While no substantial rain is in the forecast, the National Weather Service said Wednesday that a south swell featuring surf from 6 to 9 feet high is expected to arrive tonight, replacing a similarly sized swell that has been hitting the south shores for the past few days. The new swell should peak Friday night.

“This swell will be influenced by an above normal sea level, and accentuated by an above normal astronomical king tide between Thursday and Saturday,” the forecast said.

Thompson said coastal property owners and those who live in flood-prone shoreline areas are advised to take precautions to protect their assets, whether it’s through the use of sandbags, sump pumps or other means.

Boaters, paddlers and fishermen might also face unusual water levels, currents and coastal hazards, officials said.

The city of Honolulu is ready with hundreds of sandbags placed at vulnerable points at Ala Moana Beach Park, spokesman Andrew Pereira said.

Moreover, city workers on Wednesday cleared storm drains and inspected the duckbill valves that protect flood-prone Mapunapuna, he said. Those valves allow rainwater to drain into the ocean but shut off when the tide rises.

The king tides, a term used commonly elsewhere, are the highest tides of the year that normally occur around the winter and summer solstices.

Tides are the rise and fall of the ocean caused by the gravitational pull of the moon. When the sun and new moon align, their gravitational forces combine to generate the higher king tides.

But this year’s king tides are enhanced by higher-­than-normal Central Pacific sea levels caused by several factors, including climate change and other global and local influences, scientists said.

Model forecasts and satellite observations from the UH Sea Level Center and National Oceanic and Atmospheric Administration indicate high water levels will last at least through the summer.

Thompson said the June king tides are forecast to be higher than those in May, but they should look about the same because local sea levels right now aren’t being influenced by any of the Pacific’s large ocean eddies like they were last month.

“The net result is that the higher tide will actually look similar to last month’s tide,” he said.

Thompson said this year’s unusual king tides are a window into the future, when climate change-generated sea level rise will make such coastal flooding commonplace. He said the islands could see three or four such flooding tides a year by 2030 and perhaps 25 to 50 by 2050.

Joshua Stanbro, Honolulu’s chief resilience officer, said the king tides are an important learning moment and lesson for future decision-making.

“What we’re seeing with the king tides is a snapshot of the future. It’s where the normal water level will be a couple decades out,” he said. “It’s a good exercise to know where our vulnerabilities lie.”

The last of this year’s super king tides will occur about July 21-23, and the city may get the chance to learn about even more vulnerabilities.

Thompson, a research affiliate of the UH School of Ocean and Earth Science and Technology, said the July tides are expected to be the highest of the year. But what it ultimately looks like depends on surf heights, rainfall and ocean eddies, he said.

Meanwhile, volunteers with UH’s Hawai‘i and Pacific Islands King Tides Project will be out in force in the next few days documenting the flooding and high-water levels with photographs taken from across the state and around the Pacific.

Matthew Gonser, UH Sea Grant College Program extension agent, said citizen scientists over the past few years have taken more than 1,200 photographs, but the vast majority of the images were captured last month.

He said there are new photos of fish swimming in the floodwaters of Mapunapuna, the beach missing at Ala Moana and concrete bollard barriers that were pushed by the ocean water into the sand at Maunalua Bay, among other alarming pictures.

“These are warning signs of everyday conditions in some future point in time,” Gonser said.

The program is recruiting more volunteers to document the king tides for scientific research. More information on the program can be found at PacificIslandsKingTides.org.

For the latest six-day sea level forecast for Hawaii and some other Pacific islands, go to www.pacioos.hawaii.edu/shoreline-category/highsea.