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There's a big difference in daytime vs nighttime - which the BOM doesn't measure. I discovered this many years ago when I lived in Canberra, where for about 6 years I recorded daily cloud cover estimates at 3pm vs 10pm. Fourier analysis also revealed two weak correlations:
a) one correlation with the phase of the moon - clearer around first quarter to full, cloudier near third quarter to new moon.
b) a weak 6-day cycle, that is the periods of cloudy sky sort-of repeat after 6 days, a bit shy of a full week.
If you know how to read the aerological diagrams - the graphs of dew point are quite interesting while the windspeed vs altitude show wind shear and inversion layers. Add the synoptic map and you have a fair idea what's going on before even seeing the satellite photo.
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