NOAA's official ENSO status, updated monthly: Watch (El Nino likely within 6 months), Advisory (El Nino is here), Final Advisory (it has ended).
Forecasts and bulletins
NOAA's Climate Prediction Center (CPC) publishes an ENSO Diagnostic Discussion every month (usually the second Thursday) with a status line:
El Nino Watch: conditions are favourable for El Nino to develop within the next six months.
El Nino Advisory: El Nino conditions are observed and expected to continue.
Final El Nino Advisory: El Nino conditions have ended.
Not active: none of the above.
The same words exist for La Nina.
"El Nino conditions" means: a one-month relative Nino 3.4 anomaly of +0.5 °C or more, an expectation that the 3-month RONI threshold will be met, AND an atmospheric response typical of El Nino over the equatorial Pacific.
How to read it
A Watch is a forecast; an Advisory is an observation. The Advisory stays in force until conditions end, then a Final Advisory closes the event.
Why it matters for Koh Samui
As of 10 September 2026 the status is El Nino Advisory, with a greater than 90% chance of a very strong event in late 2026 and early 2027.