Tropical Highlights - September 2025

 

During September 2025, sea surface temperatures (SSTs) were below average across the central and eastern equatorial Pacific (Fig. T18). The latest monthly Nino indices were -0.2C for the Nino 1+2 region and -0.4C for the Nino 3.4 region (Table T2). The depth of the oceanic thermocline (measured by the depth of the 20C isotherm) was below-average across the central and eastern equatorial Pacific (Figs. T15, T16). The corresponding sub-surface temperatures were 1-3C below-average in the eastern equatorial Pacific (Fig. T17).

 

Also during September, lower-level wind anomalies were easterly across the western and east-central equatorial Pacific, while upper-level wind anomalies were westerly over the western and eastern equatorial Pacific (Table T1, Figs. T20, T21). Tropical convection was enhanced over Indonesia and was suppressed around the Date Line (Fig. T25). Collectively, these oceanic and atmospheric anomalies were consistent with La Nina conditions.

 

For the latest status of the ENSO cycle see the ENSO Diagnostic Discussion at: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/index.html