Discussion: Last week, the Nino SSTA regions were warmer (Fig. 1). Three of the four Nino SSTA regions remain within the La Nina threshold. The Nino34 SSTA is -0.9C which is moderate-strength La Nina but slightly warmer than the previous week. The primary diagnostic supporting weakening of La Nina is the sharp warming process in the subsurface Pacific equatorial region east of the Dateline (Fig. 2). During November, Pacific decadal oscillation (PDO) and multi-variate ENSO index (MEI) each stayed strongly supportive of the La Nina climate maintaining strength and continuing. However, the still-strong La Nina-like MEI has an attendant analog forecast that (similar to the Nino34 SSTA) indicates an ENSO phase change in 2023 (Fig. 3).
Fig. 1: The 12-week Nino SSTA observations. Note the much warmer change off the northwest coast of South America.
Fig. 2: Monthly subsurface equatorial Pacific Ocean temperatures for the past year. A warming trend has developed.
Fig. 3: Using multivariate ENSO index, an analog forecast for 2023 reveals an ENSO phase change.