[bbayer]

I am wondering how wind directions are calculated? Is there a realistic model that uses height maps and fluid dynamics or just a simple one for visual purposes?

[timedivers]

There are many different models, all of them taking into account terrain data, laws of physics and much more: https://en.wikipedia.org/wiki/Numerical_weather_prediction

[Brakenshire]

Does that mean you can possibly also get indications of gusting in direction as well as speed from the terrain? That would be really useful for sailing, particularly inland. Or maybe that's a more local effect, and beyond the resolution of these models?