El Nino Watch
The atmosphere's side of El Nino: weaker trade winds and more rain clouds near the dateline.
Indices
Monthly NOAA CPC indices: 850 hPa (about 1.5 km up) trade-wind anomalies over the west (135E-180W), central (175W-140W) and east (135W-120W) equatorial Pacific, the 200 hPa zonal wind anomaly (165W-110W), and the outgoing long-wave radiation (OLR) anomaly at 160E-160W. Series trade_wind_850_wpac_anom, trade_wind_850_cpac_anom, trade_wind_850_epac_anom, zonal_wind_200_anom (m/s), olr_dateline_anom (W/m2). Each point also carries the standardized value in meta.
Limits. Monthly, from a reanalysis; one month's value can be noisy.
Trade winds are counted positive when they blow from the east, so a negative anomaly means weaker trades (westerly anomaly), typical of El Nino. Negative OLR anomaly = colder cloud tops = more rain clouds near the dateline, also typical of El Nino. August 2026: central Pacific -6.3 m/s (standardized -2.5), OLR -14.9 W/m2.
As long as the trades stay weak, the ocean keeps its heat and El Nino persists; a return of strong trades is an early sign of the end.