Moderate El Nino
Data current through May 2026. Source: NOAA CPC.
Where are these measured?
The four Nino regions are fixed boxes in the equatorial Pacific. The SOI is the pressure
difference between Darwin and Tahiti: when it goes strongly
negative, trade winds weaken and warm water spreads east — the ocean and atmosphere are
reinforcing each other. Nino-3.4 is the primary ENSO index (El Nino threshold: +0.5 °C).
Current conditions
Nino-3.4
+0.94 °C
Primary index / El Nino above +0.5 °C
Nino-1+2
+1.81 °C
Far eastern Pacific
Nino-3
+1.14 °C
Central-east Pacific
Nino-4
+0.98 °C
Central Pacific
SOI (May 2026)
-0.9
El Nino below -8
Prob. Very Strong
63 %
NOAA CPC / NDJ 2026-27
Forecast decay to neutral
June 2027
First month Nino-3.4 forecast below +0.5 °C
EP vs CP: not all El Ninos are the same. In an Eastern Pacific event the warmth
sits off South America (Nino-1+2 and Nino-3); in a Central Pacific event it pools near the
dateline (Nino-4). Right now Nino-1+2 (+1.81 °C) is running 1.8x
Nino-4 (+0.98 °C) — a strong EP signature, consistent with 1997-98.
EP events tend to be stronger and longer-lived than CP events.
Historical context: ONI since 1950
Every El Nino and La Nina in the observational record. Use this to see how frequently
events occur, how long they last, and how intense they get. The four annotated peaks are
the events most comparable to 2026.
ONI = 3-month running mean of Nino-3.4 SST anomaly. Source: NOAA CPC.
Historical analogues
Ranked by how closely each past event's Nino-3.4 evolution matches 2026 over the first
12 observed months, aligned from precursor July.
#1
2023–24
Peak ONI: 2.0 °C / EP-type
similarity: 0.93
#2
1997–98
Peak ONI: 2.4 °C / EP-type
similarity: 0.91
#3
2002–03
Peak ONI: 1.3 °C / CP-type
similarity: 0.84
Solid lines: observed monthly Nino-3.4 anomaly. Dashed blue: NOAA/IRI forecast.
Month 0 = July of the precursor year.
Nino-1+2 (far eastern Pacific, off Ecuador and Peru) leads and amplifies EP
events. The 2026 acceleration from -0.3 °C in March to +1.81 °C in May is among the fastest
on record for this region. Dashed blue: estimated from Nino-3.4 forecast using typical EP ratios.
Negative SOI = weaker trades = more warming. NOAA monthly SOI.
El Nino threshold: -8. La Nina: +8.
Full analogue ranking
All confirmed El Nino events since 1950, ordered by Pearson correlation of the first
12 months of Nino-3.4 evolution.
Similarity captures shape, not magnitude. EP/CP type and subsurface
precursors are separate dimensions not reflected here.
What's coming
Kelvin waves (subsurface): three downwelling Kelvin waves in late 2025 and early
2026 loaded the thermocline and are the primary subsurface driver of this event. Quantitative
depth-section data (GODAS/TAO-TRITON) would show this clearly but is not yet integrated here.
Warm Water Volume (WWV): the volume of water above 20 °C averaged over
5S-5N, 120E-80W predicts peak intensity months in advance. Available at NOAA PMEL; planned addition.
OLR (Outgoing Longwave Radiation): negative OLR anomalies over the western
Pacific warm pool confirm that convection has coupled to the SST anomaly. Requires
netCDF4 or xarray; planned addition.
AMJ 2026 ONI pending: the April-May-June running mean will be the first
seasonal value fully within El Nino territory and will sharpen the intensity estimate.
Sources