The Sub-Tropical High-Pressure Ridge
1. The Hadley atmospheric circulation cells ensure that the Earth is surrounded by two broad bands of high-pressure roughly located 30 degrees north and south of the Equator. These bands of high pressure are known as the Sub-Tropical High-Pressure Ridge (STHR).
2. The peaks of the STHRs slowly drift from north and south with the seasons.
3. During the Southern Hemisphere Winter (in July), the peak of the STHR is located at roughly 27 S.
4. On average, the centre of the STHR moves south by six degrees to 33 S during the height of the Southern Hemisphere Summer (i.e. January), with the peak of the pressure ridge moving as far as 42 to 43 S during the latter half of summer (i.e. February).
The Semi-Permanent High-Pressure Cells in the STHR
1. During the summer months (DJF), there are four semi-permanent high-pressure cells embedded within the Southern Hemisphere STHR. The first is centered on the island of Tahiti in the South Pacific, the second is centered on the island of Tristan Da Cunha in the South Atlantic, the third is located off the west coast of Australia in the Indian ocean, and the fourth is located off the South Eastern coast of Australia. The latter is often split between the Tasman Sea and the Great Australian Bight with the relative strength and location of the two cells changing over time.
2. Wilson  has shown that variations in the latitude anomaly of the peak of the summer (DJF) STHR over Eastern Australia exhibit the same period and phase as that of the 18.6-year draconic spring tidal cycle.
3. In essence, what this means is that, on average, the latitude of the peak of the STHR moves back and forth in latitude by one degree between the years where the Line-of-Nodes of the lunar orbit points directly towards or away from the Sun at the time of Perihelion, and the years where the Line-of-Nodes is at right angles to the Earth-Sun line at the time of Perihelion.
This may not seem like much, but it does represent a shift of at least 100 kilometers in latitude and it can become important when it is combined with longitudinal shifts in the relative location of the centre of the semi-permanent high off SE Australia.
4. Support for the lunar influence upon the latitudinal shifts of the summer STHR is provided by the fact that the -12.57 μsec change in the length-of-day (LOD) associated with the 18.6-year Draconic lunar tides could be explained if the mass of air above 3000 m in the STHR (of both hemispheres) is systematic shifts backward and forward in latitude by one-degree over a period of 18.6 years.
5. Wilson and Sidorenkov  used the longitudinal shift-and-add method to show that there are westerly moving N=4 standing wave-like patterns in the summer (DJF) mean sea level pressure (MSLP) anomaly maps of the Southern Hemisphere between 1947 and 1994. They showed that the standing wave patterns in the MSLP anomaly maps circumnavigate the Earth with periods of 36, 18, and 9 years [moving at 10, 20 and 40 degrees west per year, repectively]. Wilson and Sidorenkov  claim that the N=4 standing wave patterns in the MSLP are just long-term lunar atmospheric tides that are produced by the 18.6-year lunar Draconic cycle.
6. For example, figure 6 a-c from Wilson and Sidorenkov  displayed below shows that, as result of these tidally driven atmospheric standing waves, a large negative anomaly of atmospheric pressure passed from east to west through the Great Australian Bight on or around the year 1971 moving at about 10 degrees per year towards the west.
7. It does not take much to realize that such slow-moving longitudinal atmospheric anomalies being driven by the 18.6-year Draconic lunar tidal cycle would have a significant effect upon the relative strength and location of the semi-permanent high-pressure cells located in the Tasman Sea and the Great Australian Bight. This is particularly true given that these longitudinal changes in the relative strength and location of the semi-permanent high-pressure cells are being matched in period and phase by corresponding changes in the latitude of the peak of the STHR (Wilson 2012).
8. Hence, it very likely that changes in the temperatures and rainfall experienced over the SE corner of the Australian continent should exhibit periodicities that match the 18.6-year lunar Draconic tidal cycle.
9. This 18.6-year pattern shows up in the annual rainfall anomaly of Victoria between 1900 and 2013.
10. This is confirmed by the following graph of the normalized auto-correlation of the Victorian rainfall (positive) anomalies between 1900 and 2017.
Please read the following three blog posts:
What is the Australian Bureau of Meteorology Trying to Hide?
A 2013 Prediction of Severe Drought in South-Eastern Australia in 2019, Willfully Ignored by the Australian Government.
Another 2013 prediction that the temperatures in SE Australia would be above normal in 2019 - Completely ignored by the Government!
Wilson I.R.G. Lunar tides and the long-term variation of the peak latitude anomaly of the summer Sub-Tropical High-Pressure Ridge over Eastern Australia. Open Atmos Sci J 2012; 6: 49-60.
Wilson I.R.G. and Sidorenkov N.S., Long-Term Lunar Atmospheric Tides in the Southern Hemisphere. Open Atmos Sci J 2013; 7: 51-76
Congratulations on another very interesting post.
Some graphs showing correlation with actual data will be very useful. Perhaps you have shown this elsewhere, and I have not seen it.
Will this periodicity show up in Southern Africa as well?