Once upon a time the Civil Aviation Act Part II Section 9 stated that CASA had safety oversight of the Aviation related functions of the Bureau of Met (and AMSA for aviation search and rescue) in precisely the same way as CASA has safety oversight of Airservices and all the aerodromes.
BUT then the responsible CASA Manager said, well if we have these powers we had better at least go and audit the Met Bureau and ask them how they explain this (long list) of safety related forecasting failures. Forecast of CAVOK but thunderstorms closing a runway with flooding was one example.
Instantly there was a huge kerfuffle and much consternation at Departmental Head level. Nobody who worked for one Minister was about to demonstrate the shortcomings of a portfolio administered by another Minister.
And so the Civil Aviation Act was amended to avoid such safety oversight. So much for safety first. And Met gets away with a great many errors because nobody says "please explain".
Those who wish to check it are welcome to go back through the amendments to the Act at
Civil Aviation Act 1988