Sunny, see GreenGhost39’s post.
The rule that causes the grief at Sydney is the forecast maximum crosswind on 16/34. ATC goes to single runway ops. when the crosswind is nowhere near aircraft operating limits. In Melbourne a 21 knot southerly with a 6 knot tailwind on 27 will mean 45 minutes COBT delay plus airborne holding for a CBR-MEL flight. Given the magnitude of the mayhem these rules cause on a routine basis isn’t it possible that the rules are a horses ar#e? Maybe its just me.