La Nina Gaining Strength

Climate Impact Company Weekly ENSO Climate Diagnostics

Issued: Monday November 17, 2025

Highlight: La Nina gaining strength.

Discussion: La Nina suddenly displays life with notable strengthening during the past 1-2 weeks (Fig. 1). All Nino SSTA regions are within the La Nina threshold. The catalyst to the cooler change is a consistent and strengthening positive phase of the southern oscillation index (+SOI) causing a steady increase in up-welling trade winds and shifting the global climate convincingly into a cold ENSO regime (Fig. 2). The subsurface cool fuel to sustain La Nina has suddenly increased during early-to-middle November after almost disappearing in October (Fig. 3-4).

Fig. 1: The 12-week Nino SSTA trend indicating all within the La Nina threshold during the past week.

Fig. 2: The southern oscillation index has shifted positive and gained intensity during November.

Fig. 3-4: Upper ocean heat analysis reveals a much cooler signature on Nov. 9^th as the warmth east of the Dateline on Oct. 20^th dissipated.