Warming East Pacific Leads to Wet Climate Bias Western South America

Fig. 1-4: The monthly upper ocean heat anomalies across the equatorial Pacific Ocean for the past 12 months, zonal wind anomalies across the eastern tropical Pacific for the past 2 months, daily Nino12 SSTA, and 30-day percent of normal rainfall in South America.

Discussion: During FEB/MAR 2025, the upper ocean heat anomalies across the equatorial Pacific Ocean warmed dramatically (Fig. 1). The dramatic warming followed a cool peak in support of the 2024-25 La Nina episode. The warming was enabled, in part due to a 2-month long period of dissipated trade winds across the tropical East Pacific off the northwest coast of South America (Fig. 2). The subsurface warming was accompanied by an El Nino-like warming of the Nino12 SSTA region where daily analysis reveals a robust 1.36C warm anomaly (Fig. 3). One influence on climate brought on by the warming waters off the northwest coast of South America is a wet bias during the past month across western South America compensated for by an enhanced dry climate in Brazil (Fig. 4) enhancing drought.