Helicity is simply a measure of the amount of rotation found in a storm's updraft air. If there is significant rotation in a storm's updraft air, the storm will more than likely become a supercell and possibly spawn one or more tornadoes.

What is updraft helicity?

Updraft helicity is defined as the vertical integral of the product of vertical velocity and vertical vorticity between two levels and is commonly used as a proxy for mid-level rotation in simulated supercells. ... Updraft helicity is most commonly calculated between 2-km and 5-km above ground level (AGL).

What does helicity mean in weather?

Helicity. A property of a moving fluid which represents the potential for helical flow (i.e. flow which follows the pattern of a corkscrew) to evolve. Helicity is proportional to the strength of the flow, the amount of vertical wind shear, and the amount of turning in the flow (i.e. vorticity).