For what it is worth I am no fan of this company however on another thread about the fuel mayday incidents it is reported that the Ryanair Captains did indeed uplift MORE than the minimum fuel figure.
In other words they looked at the weather and took EXTRA to account for this. A combination of factors including weather and ATC all had their part to play.
For information they were not the only airline to divert and subsequently have a long routing resulting in a low fuel situation. They did not land with far less than final reserve unlike another airline.
Links on the other thread to official reports etc.