These SST anomalies are produced by the periodic reinforcement of the four semi-permanent high pressure cells that are located in the Southern Hemisphere's Sub-Tropical High Pressure Ridge, as shown in figure 1. The standing wave pattern reappears roughly once every 8 - 9 years in parallel sequences that are shifted with respect to each other by ~ 3 years.
Figure 2 shows the zonal pressure anomaly profiles for some of the more prominent zonal N=4 standing wave-like patterns between 1976 and 2010.
Columns A and B of table 1 below identify all of the major zonal N=4 standing wave-like events since 1947. with the last two being in 2007 and 2010.
If the observed periodicity were to continue, you would expect to see the N=4 standing wave pattern in the SST and MSLP anomalies to re-emerge in months of December-January-February 2014-15 and 2017-18. It now appears that this is indeed the case.
Here it is in mid-January 2015:
and it is just starting to appear (roughly 3 years later) in December 2017:
The zonal N=4 standing wave-like pattern in the MSLP anomaly is being produced by lunar-induced atmospheric tides that circle the Earth roughly once every 18 years. These tides periodically re-enforce the strength of the four semi-permanent high pressure cells in the sub-tropical high pressure ridge (during the Southern Summer months of December-January-February) that produce localized heating of the SST's on their western sides. The semi=permanent pressure cells are normally located over NZ, and the eastern South Indian, South Atlantic and South Pacific Oceans.
Here we have proof of the effect of astronomical influences (in this case the lunar atmospheric tides) upon the Earth's climate.
SST Anomaly 19/12/2017 showing the prominent N=4 standing-wave like pattern. Four "H" symbols are superimposed on this plot to show the location of the enhanced semi-permanent high pressure cells in the Southern Sub-Tropical High Pressure Ridge.