Foot-High Seas Poised To Slam California

Forecasts say a train of deep Pacific “Kelvin waves” will push West Coast sea levels 6 to 12 inches higher, stacking the deck for more coastal flooding this fall and winter.

Story Snapshot

Scientists expect a 6 to 12 inch sea-level boost as Kelvin waves reach the shore.
National Oceanic and Atmospheric Administration notes about 6 inches is commonly measurable at gauges.
Higher baseline water plus tides and storms can worsen flooding and erosion.
Local crews are adding sand and preparing beaches ahead of the rise.

What Kelvin waves are and why they raise sea level

Researchers describe Kelvin waves as long pulses of warm water that slide along the equator, then turn and move north along the West Coast during El Niño. These waves do not look like surf. They ride below the surface and lift the average water level along the coast by several inches. Tide gauges and satellites can detect this rise. The National Oceanic and Atmospheric Administration reports these waves often add about 15 centimeters, or 6 inches, to sea level.

Journalists and scientists say the current event could push water levels between 6 and 12 inches above normal along parts of the West Coast. That upper bound shows up in several forecasts and reports and reflects a stronger warm-water pulse this season. The Associated Press, citing forecast discussions, reports that sea levels will begin to rise by up to a foot as the waves arrive and move north along the shoreline during October.

How a few inches can become damaging floods

Public warnings focus less on the wave itself and more on what it sets up. A higher baseline makes every high tide, storm surge, or large swell ride in on a raised platform. Forecasts caution that starting six inches higher can turn a nuisance tide into flooding at doorsteps, and a routine storm into a beach-eating event. The Associated Press notes that this stacking effect increases risks for erosion, overwash, and road closures when storms coincide with peak tides.

Officials along parts of the coast are moving fast to reduce damage. Crews are placing emergency sand on vulnerable beaches to buffer waves and protect low-lying areas. These steps do not stop the ocean from rising, but they can buy time when tides and storms peak. These actions match earlier El Niño playbooks, where temporary dunes and sand berms have helped keep water out of homes and businesses during winter storms.

Where science is confident and what remains bounded by forecasts

Scientists have strong evidence that Kelvin waves linked to El Niño elevate coastal water levels by several inches and raise flooding risks. The National Oceanic and Atmospheric Administration explains the physical mechanism and the typical size of the sea-level bump, about 6 inches, observed by instruments. Multiple outlets cite forecasts that this season’s anomaly could reach 6 to 12 inches in some areas, which would place extra stress on beaches, bluffs, and harbor fronts during storms.

Sea levels along the West Coast will begin to rise by up to a foot this month as pulses of warm water called Kelvin waves hit the shoreline and move north, sparking concerns about beach erosion and flooding in areas already impacted by climate change and El Niño.…

— PBS News (@NewsHour) October 3, 2026

The exact height and timing will vary by location, local winds, and storm tracks. The 12-inch top end comes mainly from forecast ranges shared in news reports and expert briefings rather than a single public technical memo. Still, the core message is actionable: expect higher water for weeks to months, plan for bigger impacts on king tide days, and protect spots that already flood. Communities that prepare now will face fewer costly surprises when the first strong storm lines up.