El Niño and California's sea level, 2026

No. 1 / California / October 2026

Why California’s sea level is high 3 Editorial
Kelvin waves along the equator 4 The equator / Satellites
Pacific sea level on 28 October 5 Map
How the high water traveled up the coast 6 The coast / Tide gauges
Ten tide gauges from the Galápagos to Kodiak 7 Tide gauges
San Diego compared with past strong El Niños 8 A record since 1906
Bluff erosion in north San Diego County 9 Del Mar to Encinitas
How high surf reaches the tracks 10 San Clemente / Interactive figure
Why the rail line keeps closing 12 Del Mar to San Clemente
What the agencies expect 13 CPC, IRI and NASA JPL
Sources 14 By page
How this report was made 15 Methods and credits

At a glance / 29 October 2026

San Diego, the week’s mean against its past year: +25 cm
San Diego in September, against the usual for the month: +16.9 cm
The equator from 150°W to South America, late October: about +20 cm
The western tropical Pacific, late October: about −10 cm
Speed of the swings up the coast from San Diego: 2.0 m/s
Niño 3.4, NOAA’s latest reading: +2.1°C

Sea level with the tides taken out. Pages 3 to 8.

How the water got from the equator to the coast

1The trade winds weaken; westerly winds blow over the western and central equatorial Pacific: 8 Jul – 6 Aug
2Kelvin waves carry the piled-up warm water east along the equator: 2–3 m/s
3Sea level stands high in the eastern Pacific and low in the west: +20 / −10 cm
4At the Americas the waves turn and travel up the coast: 2.0 m/s
5California’s tide gauges read high, with the tides taken out: San Diego +25 cm
6Tides and swells start from that higher sea level; on 7 September the tide stood above its prediction: +20 cm
7Waves reach the tracks and the foot of the bluffs; the rail line closes: Aug, Sep, Oct

Pages 3 to 12. The same shift in the winds moves rain and storms far from the Pacific; the agencies’ outlooks are on page 13.

Sea levelBluff erosionInfrastructure

Editorial / The equator to the coast

Why California’s sea level is high this fall

The ocean mechanics behind what the news showed this summer and fall.

Bluegraph

Bluegraph / The equator in section / The thermocline divides warm water from the cold below

This summer and fall the news from the California coast was of water where it doesn’t belong. Trains between Oceanside and Laguna Niguel stopped for high tides in August; in September waves broke over the tracks at San Clemente and carried off the rock that protects them; in late October service stopped again.^{18, 19, 21} The reports named El Niño and rising seas. Both are part of it, but they work on very different time scales, and the extra water came from the far side of the Pacific.

The tropical Pacific isn’t level. The trade winds blow from east to west along the equator and pile warm surface water against Indonesia, where sea level is about half a meter higher than off Ecuador.¹ Below the surface the thermocline, where warm water gives way to cold, tilts the other way: deep in the west, close to the surface in the east, where cold water wells up along the equator.

When the trades weaken, or turn around for a few weeks, the slope relaxes. The water doesn’t pour back like a river. It travels east as a Kelvin wave, a broad, low swell of the ocean surface that moves along the equator at 2 to 3 meters a second² and takes two or three months to cross the ocean. The thermocline sinks as it passes, and the eastern Pacific, cut off from the cold water below, warms.

This year the westerlies came in midsummer. From 8 July to 6 August the low winds over the western and central equatorial Pacific blew from the west,³ and by late July the water 50 to 150 meters down, between 150°W and South America, was more than 8°C warmer than usual.⁴ By late October sea level along the equator stood about 20 cm above its past year from 150°W to the coast, and about 10 cm below it in the west.

A Kelvin wave can’t cross a coast. At the Americas it turns and runs north and south along the shore, and the tide gauges feel it. On 29 October San Diego’s gauge stood 25 cm (10 inches) above its average for the past year, as a week’s mean with the tides taken out, and La Jolla’s 27 cm. Part of that is the season: California’s coast stands highest in late summer and fall in any year. Set against the usual for each month, San Diego’s September was 16.9 cm high, higher than in September of any of the three strongest El Niños of the past half century.

Higher sea level doesn’t flood a coast by itself. It raises the level from which the tide, storm surge and waves start, so the same tide and the same swell reach farther. On the evening of 7 September, La Jolla’s tide stood 20 cm above its prediction when a 2-meter swell arrived from the south. The pages that follow trace the water from the equator to the coast, and then to the beaches, the bluffs and the rail line.

The equator / Satellites / May to October

Kelvin waves along the equator

Bluegraph / Satellite sea level, 2°S to 2°N / Averaged by week and by 4° of longitude

Each row of the chart is a week, from early May at the top to late October at the bottom, and each column a stretch of the equator 4° of longitude wide, from Indonesia on the left to the Galápagos on the right. A filled dot is sea level higher than its own past year, an open ring lower; the larger the mark, the bigger the difference.

In May sea level stood a few centimeters high in the west, near 140°E. Through the summer the high water moved east, and by August it lay beyond the date line. By late October the equator from 150°W to the coast of South America stood about 20 cm above its past year, while the west had fallen about 10 cm below.

The tide gauges at the far end agree. At Santa Cruz in the Galápagos, La Libertad in Ecuador and Acajutla in El Salvador, sea level ran 3 to 25 cm above its past year from May through August, the last month their records reach so far.

NASA’s Jet Propulsion Laboratory, which follows the same satellites, describes Kelvin waves carrying high sea levels up and down the west coast of the Americas. With the long-term rise taken out, it finds the 2026 event as large as or larger than 1997–98 so far, with sea level 15 to 20 cm low around Indonesia and northern Australia. By a sea-level index that keeps the rise in (Hamlington and others, 2019), 1997 and 2015 were larger at the same time of year.⁵

See page 8.

Map / Satellites and tide gauges

Pacific sea level on 28 October

Sea level was high along the Americas from Ecuador to Washington and low across the western tropical Pacific.

Bluegraph

Bluegraph / Sea level from satellites, every 2° / Tide gauges, the week’s mean

Every dot is a square of ocean 2° on a side on the satellites’ last day, 28 October: filled dots are higher than their past year, rings lower. The squares are tide gauges, with their mean for the week to 29 October in centimeters. The gauges measure at the shore; the satellites, over open water.

The high water reaches north to Neah Bay, at the mouth of the Strait of Juan de Fuca, 18 cm up. Kodiak, in the Gulf of Alaska, stood 22 cm low, as did the islands of the western Pacific: Guam 19 cm, Kwajalein 20 cm.

See page 6.

The coast / Tide gauges / San Diego to Oregon

How the high water traveled up the coast

Bluegraph’s globe looking down on the coast of North America in October 2026, with tide gauges lit along the shore from California to Alaska and high sea level offshore. — **The coast / October**Tide gauges on Bluegraph’s globe

When the equatorial wave meets the Americas, part of it turns north and travels up the coast as a coastal-trapped wave, with the shore on its right. A tide gauge records it as a rise and fall of the water that has nothing to do with the tide.

Bluegraph compares the swings at each gauge up the coast with San Diego’s, day by day from May to October, and finds the delay that lines them up best. Santa Barbara keeps step on the same day. Port San Luis, Monterey and San Francisco follow a day later, Point Reyes two days, Arena Cove three. Humboldt Bay and Crescent City are eight days behind, and Port Orford and Charleston, in Oregon, nine. Along the whole coast that comes to about 173 km a day, or 2.0 meters a second.

The match weakens to the north, from a correlation of 0.9 at Santa Barbara to about 0.3 in Oregon. Bluegraph’s Sea level page keeps this comparison up to date.

Bluegraph / Days after San Diego / By distance along the coast

Tide gauges / Galápagos to Kodiak

Ten tide gauges from the Galápagos to Kodiak

Each gauge’s weekly mean compared with its own past year from May to October 2026, with the tides taken out.

Bluegraph

Bluegraph / The equator’s gauges from the University of Hawaii Sea Level Center, through August / The rest from NOAA CO-OPS

See page 8.

San Diego / A record since 1906

San Diego compared with past strong El Niños

San Diego’s tide gauge has measured the bay since 1906, one of the longest records on the West Coast. Bluegraph takes out its long rise, 2.4 mm a year, and compares each month with the usual level for that month. What’s left shows how high sea level stood for the time of year.

In the three strongest El Niños of the past half century, 1982–83, 1997–98 and 2015–16, San Diego’s sea level rose through the fall and stayed high into winter, peaking 17 to 18 cm above usual between October and January.

2026 has run ahead of all three. June and July were 6.5 and 6.8 cm above usual, August 9.6 and September 16.9: higher than any of those years in September (8.9, 9.6 and 16.1 cm), and within about a centimeter of their peaks. October’s figure waits for the month’s end. Bluegraph’s Sea level page keeps this chart up to date.

Bluegraph / San Diego, 9410170 / Monthly means from NOAA CO-OPS

Higher sea level doesn’t flood a coast on its own. It raises the level from which the tide, storm surge and waves start, so the same high tide reaches farther up the beach and the same swell breaks closer to the bluffs. The highest tides of the year, the king tides, come to California in December and January.

That is what made the last great El Niño winter so hard on the coast. After 2015–16, scientists from the U.S. Geological Survey and other institutions found that winter wave energy along the West Coast had equaled or exceeded its historical highs, and that shorelines had retreated beyond any earlier extreme, especially in California.⁶

See page 6.

Bluffs / Del Mar to Encinitas

Bluff erosion in north San Diego County

How waves at the foot of the bluffs bring them down.

From Del Mar north to Encinitas the coast is a wall of rock and sand 15 to 27 meters high. The lower cliff is Eocene sandstone, the Delmar Formation and the Torrey Sandstone. Above it, over a thin bed of loose “clean sand,” lie the sands of an old marine terrace, which settle at 26 to 35 degrees after they fail.^{7, 9}

The bluffs retreat in steps. Waves cut a notch and sea caves at the foot; the sandstone above falls as a block; then the clean sand gives way and the terrace slides after it.⁷ Over decades that averages 0.08 meters a year at Solana Beach and up to 0.15 at Encinitas,^{7, 8} but it comes in single failures. One at Del Mar in February 2021 ran more than 60 meters along the bluff and took up to 7.6 meters of it inland.⁹

Water at the foot starts it. A study of southern California’s cliffs counted the hours when the tide plus wave runup rose above 2.5 m on the NAVD88 datum, about 2.56 m above mean lower low water at La Jolla, as erosive.¹⁰ In the winter of 1997–98, when the tide, the rain and the waves all peaked, the beaches at Solana Beach were stripped and the bluff foot was notched and undercut.^{7, 10} In 2015–16, with less rain and big waves that missed the highest tides, only 12 percent of those cliffs eroded.¹⁰

The bluffs from Del Mar to Encinitas

Height, from the sand to the top: 15–27 m
Average retreat, Solana Beach to Encinitas: 0.08–0.15 m a year
Del Mar, February 2021, lost inland: up to 7.6 m
Water counted as erosive, above La Jolla’s low water: 2.56 m
Cliffs that eroded in the winter of 2015–16: 12%

From Coastal Commission staff reports and Young and others (2018).^{7, 8, 9, 10}

See page 10.

Figure / San Clemente

How high surf reaches the tracks at San Clemente

The buttons set the tide, the sea level and the waves, and the readouts add them up against the height of the rails.

Bluegraph / A composite of the rail line along San Clemente’s beaches

What the buttons show

Normal high tide: mean higher high water with summer’s usual waves, 1.0 m at 15 seconds³¹: 3.4 m
7 September 2026: the tide 0.20 m above its prediction, with 2.2 m waves at 11 seconds offshore: 4.0 m
Winter storm: this winter’s highest predicted tide, sea level 25 cm above normal and the swell of January 2010 together, as a combination rather than a forecast³²: 6.2 m
Beach erosion: the beach 1.5 m lower, and 3 m lower at the foot of the rock, which raises those three totals to: 5.0, 6.4, 7.5 m

The total is the tide, plus the water level above its prediction, plus the wave runup that 2 percent of waves top, in meters above mean lower low water at La Jolla. The rails are at 6.15 m and the crest of the rock at 5.24 m. Where the beach is already eroded, the conditions measured on 7 September put the water 0.27 m over the rails; OCTA reported waves over the tracks that night.^{19, 37}

Rail line / Del Mar to San Clemente

Why the coastal rail line keeps closing

The rail line between Los Angeles and San Diego carries Amtrak’s Pacific Surfliner, Metrolink, the Coaster and freight, and for much of the way it runs along the ocean. At Del Mar it runs along the top of a bluff 50 to 70 feet high, with the edge within 10 feet of the track in places.⁹

Del Mar’s bluff has failed under the line again and again: at two places in December 1996, four times in 2018, after rain in November 2019, and in February 2021, the failure of more than 200 feet on page 9.^{9, 11, 12, 13} SANDAG has held it for three decades: soldier piles in 1996, more than 230 columns and drainage in the first three projects, and a fifth project of about 3,800 feet of piles and tiebacks and 2,500 feet of seawalls, at about $88 million, which it reports finished this fall. Moving the tracks off the bluff is under study, with a target of 2035 in the 2021 plan.¹⁴

San Clemente / Track on the beach. Farther north the track runs on the beach itself, between the surf and the foot of the slope. Since 2021 it has closed again and again: when a sliding hillside, storm surge and erosion moved the track at Cyprus Shore by as much as 28 inches in 2021 and 2022; for slides at Casa Romantica in 2023 and Mariposa Point in 2024; and for sand and rock in the spring of 2025.^{15, 16, 17}

2026 / High tides and surf. This year the closures came from the ocean side. Service between Laguna Niguel and Oceanside stopped for forecast high tides from 11 to 14 August, and on 6 and 7 September high tides and strong waves broke over the tracks and washed away riprap.^{18, 19} On 28 September OCTA declared an emergency and planned to place about 690,000 cubic yards of sand; news reports say the governor had proclaimed one on 21 September, in preparation for El Niño.²⁰ From 26 to 30 October Metrolink suspended service between Oceanside and Laguna Niguel again, for the high tides it expected.²¹

See page 8.

Outlooks / As of late October

What the agencies expect

Outlooks from NOAA, IRI and NASA as of late October, quoted in their own terms.

Gathered with Advance Basis

NOAA Climate Prediction Center

Status, 8 October²⁵: El Niño Advisory
A strong to very strong El Niño through January–March 2027²²: > 83%
A historic event, a 3-month index of +2.5°C or more, stronger than any since 1950: September–November: 54%
October–December: 83%
November–January: 70%

With an event this strong, CPC says, the chances of El Niño’s usual effects are larger, though not guaranteed.²²

The latest ocean readings

Niño 3.4, the central Pacific²⁴: +2.1°C
Niño 3: +3.0°C
Niño 1+2, off Ecuador and Peru: +3.9°C
Relative Oceanic Niño Index, July–September²³: +1.7°C
Multivariate ENSO Index, September²⁶: 2.37

IRI and Columbia’s CCSR in mid-October

Models in close agreement²⁷: 27
Their average for Niño 3.4, October–December and November–January: near +3.5°C

Individual models differ on the peak, and IRI calls the average only a best single guess.²⁸

Sea level from NASA JPL

Against 1997–98, long-term rise taken out⁵: as large or larger
Indonesia and northern Australia: 15–20 cm low

What El Niño winters can bring

In El Niño winters the Pacific jet stream often strengthens and shifts south, giving the southern United States more chances of winter storms; it tilts the odds and guarantees nothing (CLIMAS, University of Arizona).²⁹ The extreme El Niño of 1997–98 was followed at once by the extreme La Niña of 1998–99.³⁰

Sources / By page

Sources

NOAA Pacific Marine Environmental Laboratory, “What is El Niño?” pmel.noaa.gov/elnino/what-is-el-nino
Kessler, W. S., M. J. McPhaden and K. M. Weickmann (1995), Forcing of intraseasonal Kelvin waves in the equatorial Pacific, Journal of Geophysical Research 100. pmel.noaa.gov
IRI, August 2026 ENSO Quick Look. iri.columbia.edu
IRI, ENSO forecast, CPC update, late July 2026. iri.columbia.edu
NASA Jet Propulsion Laboratory, El Niño 2026. sealevel.jpl.nasa.gov
Barnard, P. L., and others (2017), Extreme oceanographic forcing and coastal response due to the 2015–2016 El Niño, Nature Communications 8, 14365. nature.com
California Coastal Commission, 6-21-0758, Solana Beach, exhibits, with the staff geologist’s memo of November 2022. documents.coastal.ca.gov
California Coastal Commission, A-6-ENC-13-0210, Encinitas, staff report, 2016. documents.coastal.ca.gov
California Coastal Commission, CC-0005-21, Del Mar Bluffs Stabilization Project 5, staff report, 2022. documents.coastal.ca.gov
Young, A. P., and others (2018), Southern California coastal response to the 2015–2016 El Niño, Journal of Geophysical Research: Earth Surface 123, 3069. airsea.ucsd.edu
California Coastal Commission, Del Mar bluffs, January 1998. documents.coastal.ca.gov
Claims Journal, 19 December 2018. claimsjournal.com
Times of San Diego, 29 November 2019. timesofsandiego.com
SANDAG, Del Mar Bluffs Stabilization. sandag.org/delmarbluffs
OCTA, 10 April 2023, on the Cyprus Shore stabilization. octa.net
OCTA, emergency rail update, March 2024. octa.net
CBS Los Angeles, October 2021, on the Cyprus Shore closure. cbsnews.com
ABC7, August 2026, Metrolink suspends service for forecast high tides. abc7.com
OCTA, 8 September 2026, severe waves prompt temporary closure. octa.net
Metro Magazine and LAist, September 2026, on OCTA’s emergency declaration. metro-magazine.com; laist.com
NBC 7 San Diego, October 2026, high tides to suspend Metrolink service. nbcsandiego.com
NOAA Climate Prediction Center, ENSO Diagnostic Discussion, October 2026. cpc.ncep.noaa.gov
NOAA Climate Prediction Center, ENSO: Recent Evolution, Current Status and Predictions. cpc.ncep.noaa.gov
NOAA Climate Prediction Center, ENSO Diagnostic Discussion. cpc.ncep.noaa.gov
NOAA Coral Reef Watch, ENSO conditions. coralreefwatch.noaa.gov
NOAA Physical Sciences Laboratory, El Niño Index Dashboard. psl.noaa.gov
Columbia University CCSR and IRI, ENSO forecast. forecast.ccsr.columbia.edu
IRI, ENSO forecast. iri.columbia.edu
CLIMAS, University of Arizona, El Niño 2026–27 and the Southwest U.S. climas.arizona.edu
The defining characteristics of ENSO extremes and the strong 2015/2016 El Niño, NOAA Institutional Repository. repository.library.noaa.gov
NOAA CO-OPS, tidal datums for La Jolla, 9410230. tidesandcurrents.noaa.gov
NDBC station 46225, Torrey Pines Outer (CDIP 100), 2010. ndbc.noaa.gov
Stockdon, H. F., and others (2006), Empirical parameterization of setup, swash, and runup, Coastal Engineering 53, 573–588; beach slopes from USGS Data Series 602. pubs.usgs.gov/ds/602
The outlooks were gathered with Advance Basis, Global Meteorological Outlook for the 2026–2027 El Niño, 25 October 2026. advancebasis.com
U.S. Geological Survey, Santa Cruz coastal erosion, photograph by Andrew Stevens, January 2016; public domain. The cover. usgs.gov
City of San Clemente, Coastal Resiliency Plan, 2021: the railroad at 20 to 25 feet above NAVD88. sanclemente.gov
OCTA, Coastal Rail Resiliency Study, initial assessment, February 2024. octa.net
California Coastal Commission, 5-19-0288, Strand Beach, Dana Point, staff report, February 2020. documents.coastal.ca.gov
Van der Meer, J. W., and others (2018), EurOtop: Manual on wave overtopping of sea defences and related structures, second edition.

Colophon

How this report was made

Bluegraph’s measurements read alongside the agencies’ outlooks and published research on 29 October 2026.

Bluegraph

The sea-level measurements come from Bluegraph’s Sea level section: NOAA CO-OPS tide gauges along the coasts and on the islands, University of Hawaii Sea Level Center gauges on the equator, and sea level from satellites, day by day. Each gauge’s hourly water level has its predicted tide taken out and is averaged over a week, then set against the gauge’s own average for the past year.

San Diego’s long record has its rise of 2.4 mm a year, fitted from 1950, taken out, and each month is set against the usual level for that month. The delays up the coast come from matching each gauge’s daily swings against San Diego’s over the season. The equator chart averages the satellites’ daily fields over each week, between 2°S and 2°N.

The agencies’ outlooks were gathered with Advance Basis, a research system that ties every claim to its source; they are quoted here in the agencies’ terms, and their sources are on page 14. Bluegraph measures and doesn’t forecast. The bluff and the railroad come from California Coastal Commission staff reports, U.S. Geological Survey data, SANDAG and OCTA, and the papers listed with them.

The charts and the map were drawn for this issue from those numbers. The plate on page 6 is Bluegraph’s globe as it showed the coast at the end of October. The cover photograph, of El Niño surf at Santa Cruz in January 2016, is Andrew Stevens’s for the U.S. Geological Survey, in the public domain.³⁵

Continue on Bluegraph

El Niño and California’s sea level

Contents

At a glance / 29 October 2026

How the water got from the equator to the coast

Why California’s sea level is high this fall

Kelvin waves along the equator

Pacific sea level on 28 October

How the high water traveled up the coast

Ten tide gauges from the Galápagos to Kodiak

San Diego compared with past strong El Niños

Bluff erosion in north San Diego County

The bluffs from Del Mar to Encinitas

How high surf reaches the tracks at San Clemente

What the buttons show

Why the coastal rail line keeps closing

What the agencies expect

NOAA Climate Prediction Center

The latest ocean readings

IRI and Columbia’s CCSR in mid-October

Sea level from NASA JPL

What El Niño winters can bring

Sources

How this report was made