Observed 4 Oct 2026 · baseline 1991-2020 · generated 5 Oct 2026 17:07 UTC
· OISST v2.1 at 0.25° · 60°S–60°N (polar sea-ice margins excluded)
Sea Surface Temperature anomaly vs the 1991-2020 daily average for 4 Oct.
How the anomaly changed over the 7 days from 27 Sep to 4 Oct.
How the anomaly changed over the 30 days from 4 Sep to 4 Oct.
Sea surface height anomaly, 60°S–60°N, 7-day mean ending 2026-10-04.
How the 7-day mean sea surface height changed over the 7 days from 27 Sep to 4 Oct.
How the 7-day mean sea surface height changed over the 30 days from 4 Sep to 4 Oct.
Absolute: the box's SST anomaly against its 1991–2020 daily average.
Relative: the same anomaly minus the 20°S–20°N mean anomaly that day, so a tropics-wide warming does not read as El Niño. This is the basis of RONI, the official index since February 2026. RONI also rescales Niño 3.4 by about 1.18 to keep ONI-sized swings; this view shows the plain difference for every box.
OISST v2.1 at 0.25° · observed through 4 Oct 2026
The mean longitude of equatorial Pacific deep convection · OISST v2.1 · observed through 4 Oct 2026
Equatorial SST against the 1991–2020 daily climatology. Kelvin waves read as warm stripes leaning east.
Share of the 5°S–5°N band at or above the convective threshold. The ENSO Longitude Index (ELI) is the centroid of each row.
20 °C isotherm depth anomaly, 2°S–2°N.
Sea surface height anomaly, 2°S–2°N.
Phase places the last 30 days of relative Niño 3.4 (Niño 3.4 minus the 20°S–20°N mean, scaled like RONI, the official index) against warm-water volume (WWV, the heat stored above the equatorial thermocline): El Niño or La Niña beyond ±0.5 °C, recharged or discharged beyond ±0.5 standard deviations of the WWV record.
A Kelvin wave is a crest or trough in 20 °C isotherm depth, after removing the slow background (5-day mean minus 61-day mean), that has moved east at 1–3.5 m s⁻¹ over the last 15 days and is still west of 105°W. Past that it is followed to the coast (a crest at the landfall), where it splits: in sea level within 111 km of the shore, one coastally trapped wave is followed south toward Chile and one north toward California.
Percentiles rank the latest value against its full record; ocean data are Copernicus Marine analyses (WWV spliced onto NOAA PMEL's), and winds and convection are ERA5 and NOAA OLR.
Subsurface temperature anomaly, 2°S–2°N, 0–300 m, 2026-10-04.
How the anomaly changed over the 7 days from 27 Sep to 4 Oct.
How the anomaly changed over the 30 days from 4 Sep to 4 Oct.
Warm-water volume (WWV) is the amount of unusually warm water stored in the upper tropical Pacific. When it builds up, that heat tends to surface as a Niño 3.4 warming months later; when it drains away, a cooling often follows.
The dashed line is WWV shifted forward +5 months and rescaled onto the Niño 3.4 axis (r=0.55), showing how closely it has foreshadowed Niño 3.4 later in the record.
Warm-water volume before May 2022 comes from NOAA PMEL's long-term record and from June 2022 onward from our own analysis, joined with no adjustment because the two agree closely where they overlap.
Warm-water volume vs Niño 3.4, monthly means through October 2026.
Each point is one month's Niño 3.4 sea-surface temperature plotted against that month's warm-water volume (WWV) anomaly, tracing how the ocean state evolves over time.
Color marks time along the trajectory, from the start of the selected window to the most recent month, shown in red.
The shaded background marks La Niña, Neutral, and El Niño ranges by Niño 3.4.
Niño 3.4 vs warm-water volume, monthly means, latest point September 2026.
Blue over the central Pacific and red over the Maritime Continent is the El Niño convection pattern; a week is a noisy look at it, worth checking against the 30- or 90-day means.
Blue over the central Pacific and red over Indonesia is the El Niño pattern: convection has moved east with the warm water.
The 90-day mean smooths out week-to-week wobbles, showing whether the convective pattern is a sustained seasonal signal rather than a passing week.
Blue appearing where it was not, or red fading, marks convection actively shifting over the last month, not just where it currently sits.
7-day mean, ending 2026-10-01.
30-day mean, ending 2026-10-01.
90-day mean, ending 2026-10-01.
30-day change, ending 2026-10-01.
Four stacked panels on a shared time axis: the Southern Oscillation Index (SOI), 850 hPa wind and OLR anomalies averaged over the Niño 4 region, and Niño 3.4 sea-surface temperature for reference.
Vertical ticks on the wind panel mark the start of each westerly wind burst.
SOI, u850 and OLR Niño 4 anomalies against Niño 3.4, last 5 years through 2026-10-01.
Westerly wind bursts and atmosphere–ocean coupling, 2026-10-01.
Last burst: 2026-08-13 – 2026-08-18, 158°E–185°E.
Coupling index +5.17 (99th percentile of days since 1991): strongly reinforcing (heuristic).
CPC's Relative ONI, the official index since February 2026: Niño 3.4 relative to the 20°S–20°N mean, 3-month means. Shading is CPC's official episodes.
CPC's Oceanic Niño Index, 3-month means of Niño 3.4. Shading marks designated episodes: beyond ±0.5 °C for at least five consecutive overlapping 3-month seasons.
NOAA PSL's Multivariate ENSO Index: the leading mode of SST, sea-level pressure, surface winds and OLR over the tropical Pacific, in standard deviations, 2-month seasons. It has no episode rule of its own, so the shading is CPC's official (RONI) episodes.
This site's own OISST monthly record. Shading applies the ONI rule to its 3-month means.
CPC · °C · 1950 – present
CPC · °C · 1950 – present
NOAA PSL · SD · 1979 – present
OISST · °C · 1981-09 – 2026-09
1981–2026
Niño indices and SST maps from NOAA OISST v2.1 · RONI, ONI and the advisory from NOAA CPC.
Our indices use one fixed 1991-2020 baseline; CPC's ONI shifts its base
period every decade, so the two can differ by a few tenths.
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