How to simulate wind's trend from his windrose distribution?
You can't. A windrose aggregates over time, so you lose all the information about patterns over time. You're trying to do a time-based simulation, but your data source discards all time-specific information.

You need a different set of data, to base your simulation on. One that contains the dimension of time.

The changes in direction and speed over time vary hugely depending on the local climate and topology.