So, all we have to do is find that annoying butterfly and squash it, and no more tornadoes?

I prefer a more hands-on understanding of karma: Intention / intentional action. Leaving aside the point that this is what the Buddha apparently defined karma to be, it is actually useful for my practice. My present experience is influenced by what I choose to do at the moment, by the immediate consequences of what I'm doing right now, and by the consequences of what I did before (as well as many other factors which are *not* affected by my choices). And that exhausts my ability to shape the present moment. This is all I myself can do to bring about my goals, not more, but not less either.
After I had my first "oh, doh!" experience regarding this view of karma, I felt strangely disempowered. That's really all I'm supposed to be able to do? My intentions? That's all I can have a say on? But gradually, this turned into confidence: I really can do something to bring about change in my experience. The next step was to comprehend how this strange power affected other people, too: those I love, for example. My choices have an effect on them, too. So karma and sila have a real-life interaction! Who would have thought!
Not quite tornadoes, but then I'm not a relativistic quantum chaos butterfly or whatever the species is called.

Cheers,
Florian