Tropical Highlights - December 2025

 

During December 2025, sea surface temperatures (SSTs) were below average across the east-central and eastern equatorial Pacific (Fig. T18). The latest monthly Nino indices were -0.4C for the Nino 1+2 region and -0.6C 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 east-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 December, lower-level wind anomalies were easterly over the central equatorial Pacific, while upper-level wind anomalies were westerly across most of the equatorial Pacific (Table T1, Figs. T20, T21). Tropical convection was enhanced over Indonesia and was suppressed around the Date Line (Fig. T25). The equatorial Southern Oscillation index was positive (Fig. T2). 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