La Nina-like South America SSTA

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During the past several weeks a very La Nina looking SSTA pattern has emerged off the west coast of South America as the Humboldt Current is actively churning to the surface cold subsurface water and surging that chill toward the equatorial region. The influence on ENSO forecast models is to cause suppression of the weak El Nino and introduce a La Nina risk later this year.

Cold SSTA off Western South America Coast Signal La Nina Climate

Discussion: During the past several weeks a very La Nina looking SSTA pattern has emerged off the west coast of South America as the Humboldt Current is actively churning to the surface cold subsurface water and surging that chill toward the equatorial region (Fig. 1). The influence on ENSO forecast models is to cause suppression of the weak El Nino and introduce a La Nina risk later this year. Meanwhile in South America a La Nina climate pattern could evolve more quickly if the observational trend continues. During La Nina dryness tends to be most focused on Argentina. The GFS OP 15-day percent of normal rainfall forecast indicates prevailing dryness over much of Brazil and Argentina except wet weather in Uruguay (Fig. 2).

Fig. 1: A cold SSTA pattern off the west coast of South America signals increasing risk of La Nina.

Fig. 2: La Nina usually produces a dry climate in much of South America especially Argentina. Indicated is the 15-day GFS OP rainfall forecast.