The CPC ENSO Diagnostic Discussion, explained

Every ENSO status, synopsis, and probability you see on this site traces back to one document: the ENSO Diagnostic Discussion, published monthly by NOAA's Climate Prediction Center (CPC). It is the official monthly assessment of the El Nino-Southern Oscillation -- the cycle we explain here -- and the reference point for every serious ENSO tracker, seasonal outlook, and news story about the event. This page explains what the product is, what's inside each release, and how this site uses it.

What each release contains

A typical ENSO Diagnostic Discussion carries four things: a synopsis paragraph stating the current advisory status in one or two sentences; a discussion of the weekly Nino 3.4 sea-surface-temperature anomaly and the atmosphere's response; the official ONI table context (the full historical series is on our ONI & RONI index page); and a probability outlook giving the likelihood of El Nino, La Nina, or neutral conditions for each overlapping three-month season ahead. Stronger events usually get a paragraph of historical comparison, too.

When it comes out

The Discussion is released monthly, on or around the second Thursday. The timing matters because several of the underlying index tables finalize at slightly different moments -- which is exactly why ONI and RONI can disagree for the same season. When a release lands, the numbers on our dashboard refresh from CPC's feeds, a plain-language entry goes into the update log, and subscribers to email alerts get a note -- the alerts are sent editorially after a human reads the release, never auto-fired.

How to read it

Two habits make the Discussion easier to parse. First, the probability table is a likelihood for a whole season, not a forecast for any specific storm or week -- an 80% El Nino probability for JFM means eight out of ten analogous situations, not eighty percent of the winter. Second, the advisory naming follows a convention: a Watch means conditions are favorable for an event developing in the coming months, an Advisory means the event is underway, and the naming is mirrored for La Nina. The exact thresholds and index definitions are in our glossary and methodology.

How ElNino24 uses it

We are not an official source -- we read the Discussion so you don't have to, and every number we show is timestamped and traceable to CPC or IRI's public feeds (see sources). The dashboard's status banner, synopsis, and probability bars are the current release rendered honestly; the update log is our archive of what changed at each release; and the official document itself lives on CPC's site at cpc.ncep.noaa.gov.