Method

El Niño Track follows a strict pipeline: fetch → store with timestamp → render from store. Index values are never generated by an LLM.

Primary product: RONI

NOAA CPC now uses RONI (Relative Oceanic Niño Index) officially for monitoring. We prefer the public ASCII file:

• https://cpc.ncep.noaa.gov/data/indices/RONI.ascii.txt

ONI remains documented for reference:

• https://www.cpc.ncep.noaa.gov/data/indices/oni.ascii.txt

What we store

Each successful run writes public/data/enso-status.json with phase, strength, index, season, agency, product, source URL, and fetchedAt.

Phase & strength (site convention)

Mapped from CPC RONI magnitude (not an LLM judgment):

• |RONI| < 0.5 → Neutral
• ±0.5 to ±1.0 → weak El Niño / La Niña
• ±1.0 to ±1.5 → moderate
• |RONI| ≥ 1.5 → strong

Phase: RONI ≥ +0.5 El Niño; ≤ −0.5 La Niña; else Neutral.

Cache & fail behavior

We cache the store and do not hammer CPC. On fetch failure: keep the last good values and show “update failed [time]”. If there is no prior store, the UI shows a skeleton and “No stored update yet” — never a fake-looking placeholder number.

Legal

Unofficial summary of public NOAA data; not a forecast agency.