Summary (tl;dr)

A significant "Kelvin wave" — a massive, slow-moving pulse of warm ocean water — is currently impacting the Pacific coast, particularly California, leading to concerns about elevated sea levels and increased risks of coastal flooding and erosion due to an unusually strong El Niño.

Essential Background

Kelvin waves are large-scale oceanic or atmospheric disturbances that balance the Earth's rotation (Coriolis force) against a boundary, such as the equator or a coastline. Unlike typical crashing waves, Kelvin waves are subtle, slow-moving shifts in water depth or sea surface height, not visible on the surface. These waves play a critical role in the El Niño-Southern Oscillation (ENSO) cycle, where weakened trade winds in the western Pacific allow warm water to surge eastward along the equator, forming an equatorial Kelvin wave. When this eastward-moving wave hits the coast of the Americas, its energy can then propagate northward and southward along the coastlines as "coastally trapped Kelvin waves."

The Full Story

In late September 2026, concerns are mounting as a prominent Kelvin wave, driven by an abnormally strong El Niño, is making its way towards and along the Pacific coast of the Americas. This specific Kelvin wave, which scientists have been tracking via satellite since spring 2026, represents a significant movement of warm water from the western Pacific Ocean towards the eastern Pacific. After reaching the coast of South America, the wave's energy has begun traveling northward as a coastally trapped Kelvin wave, with early impacts already detected near Peru where sea levels rose by nearly six inches. It is expected to significantly affect the California coastline from late September into October, potentially elevating sea levels by 6 to 12 inches for several weeks or even months. California Governor Gavin Newsom has already declared a state of emergency in anticipation of the wave's effects.

Why It Matters

The current Kelvin wave is a critical concern because its arrival coincides with an already powerful El Niño, predicted to be one of the strongest in 1,000 years. The elevated sea levels caused by the Kelvin wave will establish a higher baseline, significantly increasing the risk of coastal flooding, beach erosion, and bluff failures, particularly when combined with high tides (such as "king tides" anticipated around Thanksgiving and Christmas) and potential winter storms. This phenomenon also leads to warmer near-shore water temperatures, which can alter marine animal patterns and negatively impact fisheries due to reduced nutrient-rich upwelling. Coastal communities that have already experienced damage from previous swells and erosion are bracing for intensified impacts.

Geographic Location

• Equatorial Pacific Ocean (origin of equatorial Kelvin waves)
• Western Pacific Ocean (warm water accumulation)
• Coast of Peru, South America (sea level rise detected)
• Coast of Colombia, South America (warm water movement detected)
• Coast of Ecuador, South America (warm water movement detected)
• Coast of Mexico (wave moving northward)
• Gulf of California, Mexico (wave path)
• Cabo San Lucas, Baja California Peninsula, Mexico (wave path)
• California, United States (expected elevated sea levels, increased flood/erosion risk, state of emergency declared)
• San Diego, San Diego County, California, United States (expected wave arrival and impacts)
• Long Beach, Los Angeles County, California, United States (past and expected flooding/erosion)
• Dana Point, Orange County, California, United States (past and expected flooding/erosion, local state of emergency)
• Laguna Beach, Orange County, California, United States (past and expected flooding/erosion, local state of emergency)
• San Clemente, Orange County, California, United States (past and expected flooding/erosion)
• Malibu, Los Angeles County, California, United States (past and expected flooding/erosion)
• Carlsbad, San Diego County, California, United States (past and expected erosion, local state of emergency)
• San Francisco, San Francisco County, California, United States (potential wave impacts)