Caspian's Fiery Maelstrom

A swirling group of fiery tornadoes leap from the ground in a 30-foot radius centered on a point you can see within range. The point must be on the ground and the tornadoes reach a maximum height of 50 ft. Until the spell ends, any creature that starts its turn there must succeed on a Dexterity saving throw or take 7d6 fire damage and be knocked prone. On a successful save, the target takes half damage and is not knocked prone.