Thanks 404T.
So you're sitting in your A3XY-Z at Brisbane, planning a flight to Hamilton Island (about 5,800' available) where the forecast and every other piece of information says it's raining heavily with a variable 5kt wind. You work out your takeoff weight based on the landing distance required in this circumstances.
What changes after you take off? Serious question, because I'm not 'getting it'.
I agree with you: The rule is pretty clear for the maximum 'dispatch' weight calculation. What I don't understand is how you 'change' anything after you take off. If it turns out the actual weather at your destination is 'better' than forecast, you can't add weight (unless, I suppose, you can somehow burn less fuel getting there than planned). If the weather is 'worse' than forecast, what then?