Shear Assessment » Helicity Storm-Relative Wind

When we compute helicity, it is most appropriate to use storm-relative winds. To find the storm-relative wind, we subtract the anticipated or observed storm speed and direction from the wind at every level of the sounding. This process requires a hodograph analysis of the wind profile to predict the storm motion.
Several methods have been proposed to determine supercell storm motion. Currently the most accepted approach is the ID (Internal Dynamics) method. Generally, storms in an environment with a clockwise-curving hodograph will move to the right of the 0-6 km mean wind, while storms in an environment with a counterclockwise curving hodograph will move to the left.
For more information on storm motion, the ID method, and supercell motion see this COMET module: