Discussion: Most climate diagnostics point toward developing La Nina as move into August. The July 2021 southern oscillation index (SOI) was ROBUSTLY positive indicating a strong La Nina climate is reorganizing (Fig. 1). The Nino SSTA regions were dramatically cooler except still warm off the northwest coast of south America (Fig. 2). Most vivid is the dramatic cooling in the equatorial East pacific subsurface during the past week (Fig. 3). La Nina is on the way, in a hurry!
Fig. 1: Monthly southern oscillation index (SOI) for 2021. Note the very La Nina-like projection for July!
Fig. 2: The 12-week Nino SSTA observations indicate a sharp cooler trend last week although Nino12 (northwest coast of South America) stays warm.
Fig. 3: Upper ocean heat in the eastern equatorial Pacific subsurface is cooling off rapidly! Here comes La Nina!