This will remain a very dangerous weather situation for the next several hours with the potential for tornadoes from eastern Tennessee and Alabama across Georgia into the Carolinas.
Tornadoes occur when strong thunderstorms start to rotate. The rotation comes from wind shear. Changing wind speed and direction in both the horizontal and vertical planes can cause an overturning motion in the atmosphere. If the air could be dyed, one would see huge rotating cylinders along the horizontal plane. When this spin is entrained into a developing thunderstorm, the axis of the rotation is lifted and becomes vertical. In turn the storm cloud itself starts to rotate. When this spin tightens in one portion of the storm, a tornado often occurs.
Story by AccuWeather.com Expert Senior Meteorologist John Kocet.