the spell itself is rather easy to make imo.
I presume the clouds around the caster is just a single custom special effect. As for the blue beam, it's not a beam, but periodically (i.e. every 0.02 seconds spawned blue explosive effects further and further from the caster
Edit: I added a map with the spell. While it doesn't look as cool as the one in your gif image, it does basically the same