Giant Pacific ‘wave’ heads for US coast as scientists warn of ‘quintuple whammy’ flooding threat

By CHRIS MELORE, US DEPUTY SCIENCE EDITOR

Published: 14:52 EDT, 19 October 2026 | Updated: 14:54 EDT, 19 October 2026

A gigantic wave barreling across the Pacific is expected to crash into the US West Coast within days, threatening homes and communities in the path.

Oceanographer Dillon Amaya from North Carolina State University said multiple Kelvin waves are moving north toward the coast, with the next one expected to reach San Diego by late October to the first week of November.

One already hit the California Coast this month and is believed to have contributed to coastal flooding and evacuations of waterfront homes during Tropical Storm Rachel.

Known as a Kelvin wave, the phenomenon is a planetary-scale wave of warm ocean water that forms when the usual tropical winds weaken during El Niño.

This lets warm water that typically piles up in the western Pacific slosh east across the equator, slamming into South America first and then moving up the coast toward the US. The result is sudden and dramatically higher sea levels of up to a foot.

The National Oceanic and Atmospheric Administration (NOAA) has warned that California could see a ‘quintuple whammy’ this year, as warmer ocean temperatures, tropical storms, high tides, Kelvin waves and climate change combine to raise sea levels and threaten thousands along the coast.

NOAA said in a statement on October 6: ‘There are one or two more that are still in the tropics.’

Amaya warned that five or six Kelvin waves typically charge across the Pacific during a strong El Niño year, an event that causes global weather patterns to flip as the ocean becomes abnormally warm.

A Kelvin wave in early October 2026 is believed to have exacerbated flooding from Tropical Storm Rachel

Oceanographer Dillon Amaya predicted a new Kelvin wave hitting the US in late October or early November

The last Kelvin wave to make its way up the West Coast is believed to have combined with the impact of Rachel, raising sea levels by several inches and making the storm’s waves and surge more damaging.

Between October 10 and 11, 2026, Tropical Storm Rachel’s remnants flooded streets and homes in places like the Long Beach Peninsula and Newport Beach’s Balboa Peninsula.

In Long Beach, waves overtopped and damaged the boardwalk, sending seawater into homes and leading to evacuations and about a dozen homes being marked as unsafe to enter.

Similar coastal flooding and erosion occurred along other south-facing beaches in the San Diego area.

‘That storm surge was almost certainly made more devastating because of the Kelvin wave,’ Amaya told NPR.

NOAA added in a statement: ‘Kelvin waves can add up to six to 12 inches, which temporarily does not pose much danger. But when there are very high tides or storm surges, their effects can be amplified because the sea level is already a bit higher.’

Amaya described this as ‘a planetary-scale wave’ which is thousands of miles across. They first crash into the northern half of South America, before bouncing northwards and rolling up the coast of Mexico and then the US.

Mark Cane, a climate scientist and professor emeritus at Columbia University, compared the waves to an ‘enormous bathtub’ sloshing during El Niño years.

Multiple homes were evactuated in Southern California as massive waves crashed into the coast in October 2026

Kelvin waves form during El Nino, hitting South America and moving up the coast to the US

‘The slosh is very peculiar, because it only goes west to east along the equator in a Kelvin wave,’ Cane noted.

AccuWeather Long-Range Expert Paul Pastelok said the El Niño that emerged this summer could be a record-breaker, surpassing similar events in 1982 and 1997, with temperatures in the Pacific predicted to rise by nearly five degrees Fahrenheit.

In the US, this warming pushes the natural jet stream flowing over the center of the country farther south, bringing moisture and storms to many southern states that rarely see snow during winter.

In the Pacific, the warmer sea-surface temperatures create the perfect recipe for more tropical storms and hurricanes to form. At the same time, the normal east-to-west trade winds weaken or reverse.

Without those usual trade winds holding the warm water in the west, the giant Kelvin waves form and slowly carry the elevated warm water eastward across the Pacific and up the West Coast.

AccuWeather forecasters have warned that the potentially record-setting heat in the Pacific this year will likely carry the effects of El Niño well into 2027, possibly affecting the climate throughout the entire year.

The next Kelvin waves are expected to arrive along the West Coast throughout the fall and early winter, according to Amaya. Typically, the waves fade before the peak of an El Niño event in early January.