The Kelvin Wave Is Here: What the Tide Gauges Show, From San Diego to Stockton

Lodi
Written By Don Bradford
The Kelvin Wave Is Here: What the Tide Gauges Show, From San Diego to Stockton

The Kelvin Wave Is Here: What the Tide Gauges Show, From San Diego to Stockton

Lodi411 - October 2026

Based on NOAA Tides and Currents and California Data Exchange Center gauge records through the morning of October 1

Summary

For a month, the 2026 El Niño's Kelvin wave has been reported as something on its way. The tide gauges show it has already arrived. On October 1, water at San Diego ran 1.21 feet above the predicted tide and Los Angeles ran 1.08 feet above it. San Francisco ran 0.79 feet above, and Port Chicago, on Suisun Bay at the mouth of the Delta, ran 0.75 feet above. All four readings were still rising.

Measured against the average of the last three Septembers, the gauges are about 11 inches high in Southern California and 6 to 7 inches high in the Bay and Suisun Bay. The signal has reached the San Joaquin River at Stockton, where the September average stage ran about 3 inches above the previous three Septembers. The September and October 2026 tide readings are NOAA preliminary data. NOAA has not yet completed its quality review, and the figures may shift slightly once it does.

The wave will not flood Lodi. What it does is raise the starting water level for every tide and storm this winter, across the Bay and into the Delta channels that drain the Mokelumne. The winter's highest tides arrive November 24–26 and December 23–25. Researchers expect two to four more Kelvin waves before spring.

What a Kelvin Wave Is, and Is Not

Along the equator, the trade winds normally pile warm water up in the western Pacific. During El Niño those winds weaken or reverse in bursts. Each burst releases some of that water as a slow eastward pulse called an equatorial Kelvin wave (NOAA Fisheries). When the pulse reaches the Americas it cannot continue east. It splits and runs north and south along the coastline as a coastally trapped Kelvin wave, keeping the shore to its right in the Northern Hemisphere (Los Angeles Times).

The wave is a bulge in the upper ocean, not a breaking wave. North Carolina State University marine scientist Dillon Amaya described it as "a bulging of the nearest 20 to 30 kilometers of the ocean that propagates up the coastline." He added: "There's no mass transport here. It's not transporting water. It's transporting a signal, and that signal is an elevated sea state" (ABC7 San Francisco). Swimmers and boaters will not notice it (Los Angeles Times). It is not a tsunami, and there is no moment when it "hits." It raises the baseline the tides ride on, for weeks or months at a time (Yahoo News, via The Sacramento Bee). NOAA puts the typical rise from one wave at 6 to 12 inches (USA Today).

How This Wave Got Here

NOAA's Climate Prediction Center logged downwelling Kelvin waves, the warming kind, starting in December 2025, January 2026, March 2026 and June 2026 (NOAA CPC, September 28 update). The milestones since then:

  • March–May: Satellite data showed raised, warmer water moving across the Pacific to just off Colombia, Ecuador and Peru. By May, seas near Peru stood nearly 6 inches above average (Yahoo News, via The Sacramento Bee).
  • May–June: Smaller pulses reached California. NOAA research scientist Nate Mantua said those impacts would likely be minor compared with fall and winter (NOAA Fisheries).
  • Late August: A larger wave reached the northern tip of South America and turned north (The Guardian).
  • September 14: The wave was off Mexico's west coast. The Los Angeles Times estimated about seven days from Cabo San Lucas to San Diego, then two to three days to Los Angeles and two to three more to San Francisco (Los Angeles Times).
  • Late September: NOAA research oceanographer Andrew Leising said the wave was "probably just reaching us now" (The Mercury News).

What the Gauges Measured in September

NOAA publishes a predicted tide for every coastal gauge. The predictions come from astronomy alone: the pull of the moon and sun. Anything the gauge measures beyond that prediction is the tide anomaly, or residual. It captures what astronomy cannot: swell, wind, air pressure, river outflow and slow ocean changes like a Kelvin wave. LodiEye computed daily average anomalies from NOAA's six-minute readings at four California gauges. They run from San Diego to Port Chicago, the last NOAA tide station before the Delta.

Water Above the Predicted Tide, September 1 to October 1, 2026

FIGURE 1. Daily average of observed water level minus NOAA's predicted astronomical tide, in feet, at four California gauges. October 1 covers readings through 9:36 a.m. Pacific time. September 2026 readings are NOAA preliminary data, subject to later quality control. Source: NOAA Tides and Currents water level and prediction records for stations 9410170, 9410660, 9414290 and 9415144. LodiEye calculation.

The chart shows two events. The first is the mid-September bump in Southern California: San Diego peaked at +1.07 feet on September 14 and Los Angeles at +0.99 feet the same day. It lines up with swell from Hurricane Marie. On September 8 that swell, on top of a 6-foot tide, flooded homes on the Long Beach Peninsula and along Dana Point's Beach Road. Laguna Beach, Dana Point and Carlsbad declared local emergencies, and Orange County activated its emergency operations center (Los Angeles Times). The bump faded within a week. The Bay Area gauges showed a smaller, less distinct rise.

The second event is the rise that began September 27 and was still climbing on October 1. It appeared at every gauge at once. It pushed San Diego, Los Angeles and San Francisco to their highest daily anomalies of the period, and Port Chicago to within 0.03 feet of its September 22 high. That fits Leising's timeline. On September 28 Daniel Swain of University of California Agriculture and Natural Resources said ocean levels off Southern California were already about a foot higher because of El Niño (USA Today). The gauges agree. Swell from Hurricanes Polo and Odalys added to Southern California water levels the same week (The Mercury News). The late-September rise is therefore not all Kelvin wave, but the Bay and Suisun Bay gauges, sheltered from that swell, rose too.

The four gauges on October 1, 2026
Gauge Above predicted tide, Oct 1 Average of last three Septembers Excess over that average Highest September reading
San Diego+1.21 ft+0.26 ft+0.95 ft (about 11 in)7.79 ft, Sept 8
Los Angeles+1.08 ft+0.18 ft+0.90 ft (about 11 in)7.43 ft, Sept 29
San Francisco+0.79 ft+0.22 ft+0.57 ft (about 7 in)7.19 ft, Sept 30
Port Chicago (Suisun Bay)+0.75 ft+0.25 ft+0.50 ft (about 6 in)5.91 ft, Sept 30

Highest readings are in feet above mean lower low water (MLLW), the average of each day's lower low tide and the zero point of a tide chart. The three-September average uses September 2023, 2024 and 2025. September 2023 was itself an El Niño month, so this baseline is conservative. Source: NOAA Tides and Currents. LodiEye calculation.

How 2026 Compares With 1997 and 2015

Any single anomaly reading carries a built-in offset. NOAA's predictions are referenced to the sea level of the 1983–2001 tidal epoch, and the ocean has risen since then. Comparing the same month across years removes the seasonal pattern. The table above shows the remaining offset in recent normal years: about a quarter-foot at these gauges.

September Average Water Above Predicted Tide, by Year

FIGURE 2. September monthly average of observed minus predicted water level, in feet. 1997 and 2015 were two of the strongest El Niño years of the modern record before 2026; 2023 was a moderate-to-strong El Niño. Years through 2025 use NOAA verified hourly heights; 2026 uses preliminary six-minute data. Source: NOAA Tides and Currents. LodiEye calculation.

September 2026 is the highest September of the six at every gauge. San Diego ran +0.84 feet against +0.73 in September 2015 and +0.38 in September 1997. San Francisco ran +0.57 feet against +0.50 in 2015 and +0.17 in 1997. Port Chicago ran +0.57 feet against +0.44 in 2015 and +0.14 in 1997. Part of the gap with 1997 is three decades of sea-level rise. Part is timing: in 1997 the coastal signal arrived later, and the bigger anomalies came in winter.

Why the Delta Gauge Matters More Than the Beach

Coastal coverage of the Kelvin wave has focused on beaches, seawalls and rail lines. For Lodi the useful question is what happens inside the Bay and the Delta in winter, when ocean levels, tides and river floods stack on top of each other. The 1997–98 record answers it.

How Strong El Niño Winters Built at the Bay and the Delta Mouth

FIGURE 3. Monthly average water above predicted tide, in feet, at San Francisco and Port Chicago during the 1997–98 and 2015–16 El Niño winters, with September 2026 shown for reference. November values and February 2016 were not retrieved and are left blank rather than estimated. Source: NOAA Tides and Currents verified hourly heights. LodiEye calculation.

In 1997–98, San Francisco's monthly anomaly climbed from +0.17 feet in September to +0.99 feet in February. Port Chicago climbed from +0.14 feet to +1.50 feet. Port Chicago sits where the Sacramento and San Joaquin river outflows meet the tide. In a wet February, storm runoff pushing out against the incoming tide raises its anomaly well beyond what the ocean alone would produce. Ocean height from the El Niño adds to that. The 2015–16 winter shows the other outcome. Its fall anomalies were high, but the Port Chicago anomaly fell to under +0.30 feet by December and January. The ocean signal alone did not carry the winter.

The lesson for Lodi: the Kelvin wave sets the floor, and the storms decide the ceiling. In September 2026, Port Chicago's average was already four times its September 1997 level. Any wet winter now starts from that higher floor.

The Signal at Stockton

NOAA has no tide-prediction station at Stockton, but the state's California Data Exchange Center records river stage on the San Joaquin River at Rough and Ready Island, on the Port of Stockton waterfront. River stage is the water-surface height at a gauge. Comparing the same station across Septembers, when river flows are at their annual low and tides dominate the reading, gives a rough local check.

  • Average stage, September 2026: 5.11 feet, against 4.97 in 2023, 4.73 in 2024 and 4.81 in 2025.
  • Difference: about 0.27 feet, or roughly 3 inches, above the three-year September average.
  • Highest September 2026 reading: 7.34 feet, against 7.08 to 7.29 in the three prior Septembers.

Stockton stage also responds to river flow, export pumping and wind, so this is a consistency check, not a clean Kelvin-wave measurement. It points the same way as the Bay gauges, slightly below Port Chicago's September excess of about 0.32 feet, consistent with a signal that weakens as it moves up the Delta (California Data Exchange Center, station RRI).

What Comes Next

No agency issues a formal probability for Kelvin waves. The forecasts that exist come from researchers and from the El Niño outlook that drives the waves:

  • More waves: Amaya expects three to four more Kelvin waves this fall and winter, and says Bay Area water levels may not return to normal until spring 2027 (ABC7 San Francisco). Swain expects two or three more (USA Today).
  • The driver: NOAA's Climate Prediction Center still gives a greater than 90% chance that this El Niño is very strong through fall and winter (NOAA CPC). CPC's September 10 discussion put the chance of a historic-strength event for October–December at 75% (NOAA CPC). The next discussion is October 8.
  • The stacking risk: NOAA's Michael Jacox said Kelvin waves are not always hazardous on their own. They do damage when they coincide with very high tides, storm surge and rain. Jonathan Warrick pointed to January through March as the months with California's biggest storms, largest waves and some very large tides (The Guardian).
Dates to cross-reference this winter
DateWhat happensWhy it matters with elevated water
October 8, 2026NOAA CPC ENSO diagnostic discussionStrength of the El Niño that generates further Kelvin waves
October 15, 2026NOAA CPC seasonal outlookWhether Northern California's wet odds are raised
November 5, 2026Full Mokelumne flood reservation due at Pardee and CamancheThe Mokelumne system's flood buffer for Lodi, Woodbridge and Thornton
November 24–26, 2026Statewide king tidesHighest astronomical tides, on top of the raised baseline
December 23–25, 2026Statewide king tides (Northern California may include December 22)Overlaps the start of the peak storm season
January 21–22, 2027Statewide king tides (Northern California may include January 20 or 23)Inside the January–March window researchers flag as highest risk

King tide dates: California King Tides Project. Reservation date: EBMUD.

The Lodi Focus

The Kelvin wave reaches Lodi only indirectly. The Mokelumne River drains through the North Delta to the San Joaquin and out through Suisun Bay. When the Bay runs high, Delta channels drain more slowly at low tide. Water levels against Delta levees stay higher through each tide cycle. The lower Mokelumne below Thornton feels the tide.

What to watch: a major storm landing during a king tide window while Port Chicago is running half a foot or more above prediction. That combination raises water against Delta levees for reasons that have nothing to do with how much rain falls in Lodi itself. Releases from Camanche are capped at 5,000 cubic feet per second when the flood reservation is encroached (EBMUD). The river's downstream outlet is a Delta whose starting level is already elevated.

None of this changes what residents should do. It changes how early they should do it. Readers can watch the same gauges this report uses:

LodiEye will continue tracking the gauges, the ENSO forecast and the Mokelumne reservation schedule through the 2026–27 water year. Readers with local observations can reach us at editor@lodi411.com.

LodiEye is the original civic-reporting and analysis arm of Lodi411.com, a citizen-run civic data and transparency platform serving Lodi, California and San Joaquin County. LodiEye gathers information of public interest, applies editorial judgment to public records, meetings, and data, and publishes original explanatory reporting for its readers — the work of a newsroom, and a representative of the news media as that term is defined under federal law. Our reporting emphasizes primary sources, public data, and full source transparency so readers can check every claim. LodiEye complements, and does not replace, the other outlets covering this region; for additional reporting on Lodi, San Joaquin County, and the broader region, we also encourage readers to consult the Lodi News-Sentinel, Stocktonia, The Sacramento Bee, CalMatters, and other established news organizations. Our full editorial standards and news-media-status statement is published at lodi411.com/editorial-standards.

This LodiEye civic climate brief was produced using artificial intelligence tools under the direction and review of the founder. Lodi411 uses multiple AI platforms in its research and publication workflow, including Anthropic's Claude (primarily Opus and Sonnet models) and Perplexity AI across a variety of large language models offered by each. These tools were used in the following capacities:

Source Discovery: AI-assisted search and retrieval identified reporting on the 2026 Kelvin wave from the Los Angeles Times, The Guardian, USA Today, ABC7 San Francisco, The Mercury News and The Sacramento Bee, along with NOAA Fisheries and NOAA Climate Prediction Center material.

Data Retrieval and Analysis: Tide anomalies were computed directly from NOAA Tides and Currents observed water levels and astronomical predictions for San Diego (9410170), Los Angeles (9410660), San Francisco (9414290) and Port Chicago (9415144). September 2026 and October 1 values use NOAA preliminary six-minute data. Earlier months use NOAA verified hourly heights against hourly predictions. Stockton stage figures come from California Data Exchange Center 15-minute records for station RRI, compared only within that station. Months that could not be retrieved are left blank, not estimated.

Presentation: AI assisted in drafting, structuring, and formatting the report, including the three inline chart visualizations and the two tables.

Final Review: Multiple AI models reviewed the completed draft for factual consistency, source attribution accuracy, arithmetic, and balanced presentation. Throughout the process, the editor sets the report's goals, scope, and tone; creates and shapes draft content; reviews and edits the report; integrates independent fact checks; and reviews the AI cross-checks and validations. Multi-tool cross-checking across independent models and sources is the primary error-reduction mechanism.

Lodi411/LodiEye believes that transparency about how our research is produced — including our use of AI under human direction — strengthens trust with readers and the broader information ecosystem. Readers who spot an error are encouraged to write editor@lodi411.com so we can correct it.

Sources

Contact: editor@lodi411.com

Don Bradford
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