Unlike the Witch, the cyclone isn't evil. It's natural, which means it just happens. An act of God. A force majeure. It comes suddenly and without warning, which can be pretty scary, but also leads the way for new things. That makes the cyclone a catalyst for change, both in terms of the landscape (Aunt Em and Uncle Henry are going to need a new house) and in terms of the character. It's no coincidence that Miss Gulch morphs into the Wicked Witch in the middle of it, or that Dorothy learns the meaning of the phrase "be careful what you wish for" at the same time.

That's why it has to be something natural, or at least without a moral agenda. Otherwise, you'd see it tilted more dramatically on the side of Team Hero or Team Villain. But because it does both good and bad things, it really doesn't take sides. Furthermore, it also stresses the fact that change is inevitable. You can't stop the cyclone with magic slippers or a magic sword or even a light saber. It can't be tricked with a clever riddle or beaten with a spell from a mystic text. It hits you, it knocks some big things around, and you basically just have to sit there and take it.

However, you can also pick yourself up, take stock, and deal with anything in your life that just got turned upside down. (Like ending up in a magical land full of dancing little people, for instance). Not everything can go your way, and the cyclone is a great way to showing Dorothy how to hop back on the horse once everything he or she knew has been blown away.

You know how it's often said that the Chinese word for "crisis" is made up of two characters meaning "danger" and "opportunity"? Unfortunately, that isn't really true, but it would be cool if it were. You could include it in your essay about The Wizard of Oz. Regardless, sometimes in life it takes something dramatic to blast us out of our ruts and make us try new things.