Eddy 3D - wind analysis not working properly

Hi,
I am trying to get some annual wind analysis of this site using Eddy 3D. I wish to create Lawson, Davenport and Nen 8100 analysis.

However, since the house in question is on top of a hill the slicing operation becomes inaccurate. (Very high wind speeds because the probings happen far up in the sky). I tried to probe using a trimmed NURBS surface that followed the topography so that I could get a more correct result. However, the probing did not work.

In general, how do you make wind studies when you have topography? I mean if the ground slope or bend or anything the hole analysis should become very inaccurate with a flat slice plane. Yet if you make the topography all flat it feels like other inaccuracies would arrive.

If someone could help me I would be so thankful!

Sam