What this is

Rebuilt from the latest readings several times a day (the time is at the top of this panel): how the 2026–27 El Niño is showing up along the California coast, set against every season since 1970. It is a student’s analysis of public data — not a forecast, not a warning system and not reviewed by any agency.

What is uncertain

• The three questions, and the answer to “Does El Niño erode California’s beaches?”, are graded by tests against 14–76 past years or winters. Every test, its 95 % range and the data it rests on are listed under “Check the numbers and sources” in the guide, with the numbers to download; where a range includes “no link at all”, the page says so rather than claim one.
• The past-winter sea-level cases replay what each gauge recorded in 1982–83, 1997–98 and 2015–16. They are history, not a prediction, and they describe still water only: waves, storm surge and rain come on top.
• The coastline colours are measured history: how each beach has sat in past El Niño winters (satellite, 1984–2025) or moved over decades (USGS). They say where the coast has given way before — not what will happen this winter, which depends on sand supply, nourishment, seawalls and storm timing.
• The wind is a model, not a measurement: NOAA’s CFSv2 winds as CSIRO’s wave hindcast carries them and, for the weeks CSIRO has not yet published, NOAA’s GFS winds — every six hours on a grid of about , this season only. A grid that coarse softens a hurricane’s strongest winds.
• Past “now” the clock shows a forecast, from one experimental model (Google DeepMind’s WeatherNext 3), seven days and no further: the streaks are the average of its scenarios’ wind, the glow the wind its windiest tenth of scenarios reach. It says where and when strong wind is possible — never a storm’s track, and not its strength, which it understates by half or more. How its flags have done this season is said beside it; the official outlook is the National Hurricane Center’s.
• The 3-D views of Torrey Pines draw measured heights and distances to true scale, but the beach’s width and slope, the bluffs and the sea floor are illustrations, and how far the waves run up the sand is an estimate (Stockdon et al. 2006), uncertain by metres — more than some of the changes it shows.
• Buoy and tide-gauge readings are preliminary when fetched; this season’s storm tracks are provisional until NOAA’s post-season review.

Official sources

• Warnings and surf / coastal-flood statements — National Weather Service: San Diego, Los Angeles, Bay Area, Eureka
• Coastal flooding and erosion projections — USGS CoSMoS, Our Coast, Our Future
• El Niño status and outlook — NOAA Climate Prediction Center

Words on this page

• An El Niño winter: the tropical Pacific at least warmer than typical from November to January (NOAA’s own threshold); a La Niña winter: as much cooler; neither: in between. Every chart and figure here counts winters this one way. A late summer is measured the same way from June to November.
• A strong El Niño: or more — the strong El Niño summers of the hurricane tests, and the year menu. The super El Niños: the three warmest winters on record.
• El Niño winters’ waves are set against a typical winter — every winter on record — as the sea level is. One study counts its own: the satellite beach study (CoastSat) marks El Niño winters by NOAA’s broader, many-variable measure, December to February, small ones included.
• Typical: the long-term average for that place and that time of year.
• Three kinds of waves, sorted hour by hour from what a buoy measured — where they come from, the seconds between crests, their height: hurricane-type swell, from the south-east to south-west (140–220°), crests 10–14 seconds apart, at least — what a tropical storm off Mexico sends; long-period south swell, from the south (160–220°), 14 seconds or more apart, at least — storms in the far Southern Hemisphere; and everything else — mostly winter’s swell from the west and north-west and waves the local wind raises. A definition, not a storm-by-storm attribution.
• Trade winds: the steady winds that blow from the east along the equator most of the year, pushing the sun-warmed water west toward Asia; El Niño begins when they slacken and the warm water slides back east (“Where it starts”, on the first map). This page holds no record of the winds.
• A Kelvin wave: a broad, slow bulge of warm water that the slackening trade winds let slide east along the equator, below the surface, two to three months to cross (NOAA); at the Americas it splits, and half runs north along the coast, lifting the sea as it passes. Tide gauges measure its footprint; no picture on this map shows the wave itself.
• Thermal expansion: water takes up more room as it warms, so a warmer upper ocean stands higher — the other way El Niño lifts our sea.
• The stack: how high the water reaches on a given day — the tide, plus the higher sea beneath it, plus storm surge and low air pressure, plus the waves running up the beach. The National Weather Service’s clip in chapter 1 walks through it.

Data and credits

• How strong El Niño is — how much warmer than typical the tropical Pacific is running, week by week and averaged over three months (NOAA’s name for the latter is the Oceanic Niño Index): NOAA Climate Prediction Center.
• Storm tracks: IBTrACS v04r01, NOAA NCEI (Knapp et al. 2010, Bull. Amer. Meteor. Soc., doi:10.1175/2009BAMS2755.1; Gahtan et al. 2024, doi:10.25921/82ty-9e16).
• Waves: NOAA National Data Buoy Center; Scripps / CDIP Waverider buoys — their data were furnished by the Coastal Data Information Program (CDIP), Integrative Oceanography Division, operated by the Scripps Institution of Oceanography, under the sponsorship of the U.S. Army Corps of Engineers and the California Department of Parks and Recreation. Water levels, tide predictions and flood thresholds: NOAA CO-OPS. Coastal water temperature: NOAA OISST v2.1.
• Wind on the map (a model): NOAA’s CFSv2 winds from Durrant, T., Hemer, M., Smith, G., Trenham, C. & Greenslade, D. (2019), CAWCR Wave Hindcast – Aggregated Collection, CSIRO; CC BY-SA 4.0, and the wind files this site serves, condensed from it, are shared under the same licence. The latest weeks: NOAA’s Global Forecast System (its six-hourly analyses, public domain), read from Google Earth Engine’s copy of it (NOAA/GFS0P25).
• Basemap and satellite imagery: we acknowledge the use of imagery provided by services from NASA’s Global Imagery Browse Services (GIBS), part of NASA’s Earth Science Data and Information System — Blue Marble, GOES-West GeoColor (NOAA), VIIRS and MODIS. Street basemap © OpenStreetMap contributors.
• Beaches in El Niño winters: CoastSat satellite-derived shorelines — Vos, Harley, Turner & Splinter (2023), Nature Geoscience 16, 140–146; data doi:10.5281/zenodo.15614554 (CC BY 4.0), condensed here to ~ medians. Long-term shoreline and cliff change: USGS National Assessment of Shoreline Change (Hapke et al. 2006; Hapke & Reid 2007), public domain.
• Where the water reaches: NOAA Office for Coastal Management, Sea Level Rise Viewer inundation map (still water in half-foot steps over mean higher high water, on lidar elevation models), its tiles shown as NOAA draws them — NOAA’s own words: a screening-level tool, “as is”, not for navigation, permitting or other legal purposes. The high-tide line at each gauge: NOAA CO-OPS datums (1983–2001).
• The flood log under “Check the numbers”: the National Weather Service’s own log of coastal floods, storm tides and high surf (Storm Data), from NOAA NCEI’s Storm Events Database, drawn on the Weather Service’s public forecast zones (api.weather.gov); public domain.
• Sea-surface temperature against what is typical for the date (the guide’s first map): GHRSST Level 4 MUR analysis, JPL MUR MEaSUREs Project, served by NASA GIBS.
• Photographs in the tour: U.S. Geological Survey, public domain (Daniel Hoover; Christine Hegermiller), from USGS’s release on the 2015–16 El Niño winter, which also gives the 76 % figure (Barnard and others 2017, Nature Communications). News videos are embedded from their publishers’ YouTube channels and remain theirs.
• Breaker height on the 3-D beach: Komar & Gaughan (1972), Proc. 13th Coastal Engineering Conference. The shoreline the buoys’ waves stop at is assembled from the CoastSat and USGS shorelines above.
• Land outline: Natural Earth (public domain). Map library: Leaflet.
• 3-D: three.js (MIT). Torrey Pines’ beach slope: Yates et al. (2009), Table 1, from Scripps’ surveys; its waves: the Torrey Pines Outer buoy (CDIP / NOAA); how far they run up the sand: Stockdon et al. (2006).
• Torrey Pines’ bluffs, land and sea floor in 3-D: NOAA NCEI, San Diego, California Coastal Digital Elevation Model (1/3 arc-second, NAVD 88; 2012), from the 2009–2011 California Coastal LiDAR Project (Scripps’ laser survey of March 2009 where it has gaps) and NOS hydrographic surveys — “Produced by the NOAA National Geophysical Data Center. Not subject to copyright protection within the United States.” Not to be used for navigation. Its heights are set to the tide tables’ zero with NOAA’s datums for the La Jolla tide gauge (1983–2001).
• The photograph laid on Torrey Pines’ land in 3-D: USDA National Agriculture Imagery Program (NAIP), 2022 (the beach and the reserve photographed on 25 April 2022), from the USGS National Map — “USGS, USDA, The National Map: Orthoimagery”; public domain.

Privacy

No cookies, no analytics, no accounts. To draw the map your browser fetches tiles from NASA and OpenStreetMap and the map library from cdnjs — and, on the last chapter’s flood map, NOAA’s tiles from coast.noaa.gov; like any website they see your IP address. Only if you open a 3-D view does your browser also fetch the 3-D library (three.js) from cdnjs — and, from this site, the scene, NOAA’s ground and an aerial photograph: under 1 MB in all, and without the photograph when your browser asks to save data or reports a slow connection. Only while the wind is on does your browser fetch it, from this site: up to about a third of a megabyte for each month of the replay. Only when the clock goes past “now” does it fetch the forecast’s wind, also from this site: about a tenth of a megabyte. While the page is open it also asks this site every 10 minutes whether newer readings are out — a few bytes, and nothing is sent. Nothing you do here is sent anywhere else; your choice of units is remembered in this browser only. The guided tour offers a few news videos: none is loaded until you press play, and then the player comes from YouTube (Google) in its privacy-enhanced mode, under Google’s own terms.