The best way to become a lucid dreamer (to know you are dreaming while still in the dream) is to record your dreams in a diary every day. If you have recurring dreams or often dream of specific symbols - talking tornados, apple trees in snow, etc. - then these symbols are good clues with which to associate the awareness you are dreaming. Next time you are in a dream and ask yourself “What was I supposed to remember about talking tornados?” you will remember that you only talk to them when dreaming! Similarly, people who often have flying dreams and nightmares use these unusual (and impossible!) dreams with which to associate the awareness that they are dreaming.
Your idea for working with symbols while dreaming is one of the most exciting and promising areas of lucid dream research. For example, dreamers who suffer from nightmares, if they realize they are dreaming, can ask their attackers to identify themselves. “Who are you?” they ask. “What do you want?” The dream figure may answer back in cryptic dialogue or with revealing insight, or the dream itself may metamorphose into a related symbol or representation. One woman I know had recurring dreams of tidal waves smothering her until she asked the wave, in a lucid dream, to identify itself. Suddenly the dream shifted and she was a young girl again seated at a formal dinner table with her mother and a group of her mother’s friends. All of the older women sat in large chairs while she sat in a child’s chair, and appeared to be looming down upon her. This dream helped her to realize her feelings for her mother, whom she acknowledged was a domineering and controlling woman. After this dream, her nightmare of the tidal wave stopped, and her mother became concretely identified in her dreams. In the same spirit, I will be interested to hear who or what your talking tornado turns into! Good luck and I would love to hear back from you with your results.