Weak La Nina Continues

Climate Impact Company Weekly ENSO Climate Diagnostics

Issued: Monday November 24, 2025

Highlight: Weak La Nina continues.

Discussion: During November, La Nina is weak but established with both oceanic and atmospheric characteristics. The Nino34 SSTA cools to -0.8C, the strongest (cool) signature of this episode (Fig. 1). The southern oscillation index shifted to (mostly) strong positive phase during November, indicating a La Nina atmosphere has formed (Fig. 2). The subsurface cool fuel to maintain La Nina is weak-to-moderate and slightly less cool during the past 1-2 weeks (Fig. 3). The latest CFS V2 Nino34 SSTA forecast continues to indicate La Nina 2025-26 is short-lived and followed by neutral ENSO before the end of Q1/2026 with a possible El Nino developing into middle of next year (Fig. 4).

Fig. 1: The weekly Nino SSTA observations for the past 12 weeks.

Fig. 2: Monthly southern oscillation index observations from the past 12 months including the projected NOV-25 value.

Fig. 3: Upper ocean temperature anomalies analysis along the equatorial Pacific Ocean.

Fig. 4: The latest NCEP CFS V2 Nino34 SSTA forecast through August 2026.