Tornadoes can appear in many shapes and sizes. Most tornadoes occur in the form of a narrow crater (few hundred meters in diameter), with a small cloud of debris near the earth's surface. Tornadoes may be obscured completely by rain or dust. Such tornadoes are especially dangerous, as even experienced meteorologists might not see them.The reasons for the formation of tornadoes are not fully understood so far.Affecting factors Tremendous lifting force at a greater height (fall from which the person can be lethal)Captured objects (including sharp edges), flying with great speed the Destruction of buildings, communications, breakages of transmission lines the Occurrence of fires