No problem having an alternate 40NM away. In some instances where they are separated by mountains the weather patterns are completely different.
So lets say aeroplane is inbound to Sydney and their fuel policy requires an alternate at departure. Lets say that alternate (say CBR) goes u/S due unforecast FG en route. SYD is still showing CAVOK. Should that aircraft divert to BNE because they no longer have an alternate or should they continue to SYD where the weather is fine? What do VOZ do in this circumstance?
What happens when after deciding they are going to Sydney the weather at Sydney goes U/S due unforecast FG?