Hey Harrow,
I've been trying to go for a dawn sail for about a year, every time the graphs look good you go down to the water and... nothing. Other times it's blowing its ring off as the sun rises, but it was unforecast so I can't do anything about it!
I think the problem is that the forecasts don't work well at night, because not many people care about the weather then. Good luck, that would be a trip and a half if the wind's up