La Nina Suddenly Loses Intensity

Highlight: La Nina Suddenly Loses Intensity

Fig. 1: The Nino SSTA regions warmed significantly last week.

Discussion: Last week the Nino SSTA regions warmed significantly and La Nina lost intensity (Fig. 1). In the eastern equatorial subsurface robust cool water supply diminished indicating fuel to sustain La Nina is less plentiful (Fig. 2). Cool inflow at the surface from the southeast Pacific is weaker although still present while cool inflow from the northeast Pacific has not developed (Fig. 3). Normally both of these two trajectories are cool and push cool waters into the Nino4/Nino34 SWSTA regions to sustain La Nina. However, given the super warm North Pacific SSTA pattern the cool inflow (also characteristic of cool phase Pacific) failure is likely contributing to the suddenly weaker La Nina signature.

Fig. 2: The Australia Bureau of Meteorology indicates equatorial East Pacific subsurface cool waters to sustain La Nina remains present but diminished since earlier this month.

Fig. 3: Cool inflow from the northeast and southeast Pacific is normally required to sustain a strong La Nina pattern. However, cool inflow from the northeast Pacific has not developed.