This page explains what the dashboard on IAMElNino.com computes, where each number comes from, how often it updates, and where its limits are. If you intend to cite anything from this site, read this first.
What This Site Is
IAMElNino.com pulls ENSO monitoring data directly from public agency feeds and presents it in one place, with written interpretation kept clearly separate from the raw figures. The original contribution is the synthesis, the index precision and the interpretation, not the underlying observations, which are NOAA's and are freely available.
Data Sources and Update Cadence
| Quantity | Source | Updates |
|---|---|---|
| Weekly Nino region SST anomalies (relative) | NOAA CPC, rel_wksst9120.txt | Each Monday |
| Seasonal RONI | NOAA CPC RONI series, ERSSTv5 | Monthly, around the 5th |
| Seasonal ONI | NOAA CPC ONI series, ERSSTv5 | Monthly |
| ENSO alert status and probabilities | CPC ENSO Diagnostic Discussion | Second Thursday monthly |
| MJO phase and amplitude | NOAA PSL, ROMI | Daily |
| Rainfall and drought | CHIRPS satellite rainfall | Periodic |
| Subsurface and sea level | NOAA, NASA JPL | Periodic |
Live dashboard panels query these feeds when the page loads. Written summaries elsewhere on the site are static and carry the date they were current as of.
Which Index the Site Uses, and Why It Matters
NOAA CPC changed its primary ENSO classification index in February 2026, from the Oceanic Nino Index (ONI) to the Relative Oceanic Nino Index (RONI). RONI subtracts the tropical-mean SST anomaly from the Nino 3.4 anomaly and then rescales the variance to match the original index, before applying a three-month running mean.
This site tracks the relative series by default, because that is what CPC's own ENSO products now quote.
One consequence trips up careful readers. NOAA publishes two weekly Nino region tables and did not switch both:
rel_wksst9120.txtcarries the relative weekly values. This is the feed behind this dashboard.wksst9120.forcarries the conventional weekly values and was never changed.
Both are live and both are correct. In mid-2026 they differ by a nearly uniform 0.7 to 0.8 degrees Celsius across all four Nino regions, because the tropical-mean anomaly being netted out is currently that large. If a figure quoted elsewhere runs roughly 0.8 degrees above the one shown here, that is almost certainly the conventional table rather than an error. The full explanation is in our RONI versus ONI explainer.
Thresholds and Classification
- El Nino conditions: RONI at or above +0.5 degrees Celsius. La Nina: at or below -0.5. This is the same numerical threshold ONI used; what changed is the quantity, not the line.
- A historical episode requires the threshold to be met across five consecutive overlapping three-month seasons.
- CPC treats conditions as present when the monthly relative Nino 3.4 departure meets or exceeds the threshold alongside consistent atmospheric features, and is forecast to persist for three months.
The Teleconnection Analog Engine
The dashboard includes an analog scoring tool that compares the present state of the major teleconnections against every prior year in the record. Its full methodology, including feature weights, the as-of data rules that prevent look-ahead, and its stated limitations, is documented separately on the analog methodology page.
An analog year is a historical similarity, not a forecast, and the similarity score is an index produced by that algorithm rather than a probability.
Known Limitations
- Revision. Weekly values change after first posting. Recent RONI values are estimates for up to two months. A single reading is never the final word.
- Point values versus area means. A warm patch on an anomaly map is not the same as a box-averaged index. The two are frequently confused in coverage and are kept distinct here.
- Seasonal outlooks are probabilistic tilts, not predictions of any month, storm or total.
- Regional composites are small samples. Averaging three strong events does not produce a forecast.
- Model agreement is not forecast skill. Seasonal systems have never been verified against an event outside the observed historical envelope.
- This is not an official forecast. For operational guidance, consult NOAA CPC and your national meteorological service.
Corrections
Errors found in published material are corrected and logged publicly. See the corrections log and the editorial standards.