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. It is not uncommon for major tornado outbreaks or families of tornadoes to occur during the same period, causing widespread damage over an extensive area, including several states. 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 stron rotary winds and the impact and speed of airborne debris, tornadoes quickly become a destructive and deadly force. Until recently, it was believed that the drop of atmospheric pressure caused buildings to explode or collapse. The actual cause is the force of the tornado winds pushing the outward 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 have become dealy missles when driven by the force of a tornado's strond winds.