First impressions are that there is a lot of interest but the composition feels a little off.
Technically this is good. There is good detail in the horses and given the weather the tones look good. I feel that given the wind is pushing the tree left and the rain is driving left we should have a little more frame to the left - just my feeling.
Artistically this is great. The horses being buffeted by the wind and rain but still standing their ground sends a strong message to the viewer.
In summary a good shot and the 6.x score reflects that. It just lacks the final "wow" needed in a Free Study. A good shot and result even so.