I love the energy in this pic. The pose has this kinda...slow-motion, elegant feel to how she's bending back, and I like how that sense of calm contrasts with the fast-paced, frantic energy that exists in the shapes of the cloud-skirt and it's shadows, and especially in how the hair is flung and flying around. I love how your lighting not only adds drama to the pic from the purely lighting/shading angle, but also how the shapes of the shadows add a lot of depth and communicate a lot of the action and energy, too.
Awesome pic. : )