They vary from gray to black in color and can be seen when the air column contains condensation, surface dust or debris. Some exceptionally large tornadoes lack the classic funnel-shape and may appear as large, turbulent clouds or rain shafts near the ground. Occasionally, two or more tornadoes occur simultaneously, extending from the same thunderstorm. The storms claimed 315 people as they roared through 13 states. Strong winds, heavy rain, and especially large hail often precede a tornado and are clear warning signs of impending tornado formation.
Most significant tornadoes come from the southwest and move in a northeasterly direction.
Through the combined action of strong rotary winds and the impact and speed of airborne debris, tornadoes quickly become a destructive and deadly force. The actual cause is the force of the tornado winds pushing the windward wall inward, resulting in the roof being lifted up and the remaining walls falling outward. The fact is that most tornado-related deaths are caused by head injuries from flying debris. Sticks, glass, roofing materials, lawn furniture and other similar materials become deadly missiles when driven by the force of a tornado's strong winds. Demonstrating the incredible strength of a tornado's wind force, in 1931 a tornado in Minnesota carried an 88 ton railroad coach and its 117 passengers 80- feet through the air and dropped them in a ditch.