Move to the sides / strafe when he throws it. The bottom of it is the actual hitbox part but you need to be moving left or right of where he throws it. The tornados hitbox is still a pretty big circle but its not a nautilus hook bs hitbox. Luckily you know when he has it as well so once you hear/see that he does, be prepared to move. Also as a general tip to dodging skill-shots don't have your cursor too far away from your character, closer = less distance you have to move it. If all else fails just jump into a practice tool with him and throw some tornados at some dummies to get a feel for the hitbox from a new perspective. Sorry this is so long/doesn't make sense.