Atmospheric instability has two components: rising air and wind shear, which is created as wind speed changes with height. The rising air, or updraft, is essential because air cools as it moves up ...

This clash of air masses creates atmosphere instability at the boundary, where the warm and less dense air is pushed upward above the cold and denser air, creating precipitation.

CAPE is expressed in joules per kilogram (J/kg) and can range from zero to over 5000. In general, CAPE values of less than 1000J/kg represent weak instability, 1000 to 2500J/kg moderate ...

With the cap in place, air below it can continue to warm and/or moisten, thus increasing the amount of potential instability. Or, air above it can cool, which also increases potential instability.

2 key tornado ingredients, on steroids The hyperactive season has been due to an abundance of two key ingredients for tornadoes: wind shear and instability.

Tornadoes in December aren’t unusual in the Gulf Coast and lower Mississippi Valley states, but the Dec. 10-11 outbreak was extreme and far-reaching.