MEMPHIS, TN (WMC) - During severe weather coverage, you may hear the term wind shear. Wind shear is the fast changes in wind speed or wind direction in a short period of time or distance.
There are two ways shear can move, vertical and horizontally. Vertical shear moves vertically and changes with height, while horizontal shear refers to a quick change in wind speeds that happens horizontally. The three types of wind shear are directional shear, speed shear, speed and directional shear.
Wind shear is usually caused by thunderstorms. In a thunderstorm, wind moves downward at a fast speed and once it hits ground level, the wind will spread out in all directions and because the wind is spreading out at all different speeds and direction, you get wind shear. This fast downward moving winds within a thunderstorm are called down burst.
A tornado is a narrow column of rotating air that stretches from the base of a cloud to the ground.
If the cloud never reaches the ground it is a funnel cloud.
In the breakdown about hurricanes, we discussed how wind shear can tear apart a hurricane but on the flip side, it is necessary for a tornado to form. Tornadoes form due to wind shear and instability. Tornadoes form in very strong, violent thunderstorms when wind shear and instability is present.
Instability is when there is warm and humid air in the lower atmosphere and usually there is cooler air in the higher levels of the atmosphere. The collision of air masses makes for an unstable environment.