Tornadoes, nearly three-quarters of which occur within the U.S., are unpredictable and can cause massive damage. New tools and data are helping scientists learn more about when they might form and what paths they might take. ➡ Subscribe: http://bit.ly/NatGeoSubscribe ➡ Get More 101 Videos: http://bit.ly/NatGeo101 About National Geographic’s 101 Series: Explore and experience the forces that shape the world around us. Get More National Geographic: Official Site: http://bit.ly/NatGeoOffic