Why are tornado watches and warnings always shaped like a rhombus?

Question

If you don't know the answer, what a rhombus is (http://id.mind.net/~zona/mmts/geometrySection/commonShapes/rhombus/rohmbus.html), what a tornado warning is, or what a tornado watch is, DO NOT ANSWER.

The weather reports ALWAYS show tornado warning/watch areas in rhombus shapes, but I can't figure out why. This has been asked on Yahoo! Answers before, but every answer I've seen was flat wrong.

Answer 1

What is that you want no one to answer? What tornado watches and warnings are? I suppose you only want to know about the rhombus shape. Warnings are in the size of a county or even smaller than that. Watches cover a large area to signify where development MIGHT take place.