Tornados are a force of nature, and very fun to draw. This tutorial from the fine folks at Drawing Now demonstrates how to draw a tornado surrounded by flying cars and trees. Here are their step-by-step instructions:
1. First step you should do is draw 3 curve lines as the tornado form. Each line ends in one point. 2. After tornado form is done, now start to sketching out the spin lines that surrounds the shape of the twister. Add objects such as cattle, house, tree, cars, etc. to show how powerful a tornado is. Erase middle line. 3. Start to coloring, use Brush tool and choose h.appy- haha. color. Give shadow effect, choose darker gray. Color the objects. 4. Add highlights and more shadows, draw bumpy line as outline of a tornado.
Original tutorial here