Subsurface Equatorial Pacific Is Cooling As La Nina Development Has Restarted

Highlight: Subsurface equatorial Pacific is cooling as La Nina development has restarted.

Fig. 1-3: The subsurface equatorial East Pacific upper ocean heat is cooling again close to the previous (cool) peak last April and implying La Nina development is occurring. The Nino34 SSTA has cooled to -0.13C, a change of -0.55C during the past 30 days.

Discussion: La Nina development stalled during the past 10 weeks or so as the subsurface cool waters required to ignite cold ENSO lost half their April intensity. However, during the past 7-10 days, cooling has resumed indicating La Nina development has returned (Fig. 1). The Nino34 SSTA has cooled to -0.13C (Fig. 2) and appears to be trending toward the -0.50C La Nina threshold based on the 30-day change of -0.55C (Fig. 3). The atmosphere continues in flux with sharp variation in daily southern oscillation index (SOI) implying the climate pattern is in neutral ENSO phase. Based solely on the subsurface and Nino34 SSTA trend, La Nina onset may arrive by October.