2. Parameters

Shear Assessment » Helicity SREH Computation

Hodograph with arrows and shading to show the area storm-relative environmental helicity (SREH)

Automated sounding routines such as the Interactive Skew-T compute SREH from the hodograph. On the hodograph, SREH is proportional to the area swept out by the storm relative wind vector over the depth of the inflow, typically 3 km AGL, as depicted in this figure. SREH values are positive for right-moving storms, characterized by clockwise-curving hodographs (as shown here) and cyclonic rotation, while SREH values are negative for left-moving, anticyclonic-rotating storms with counterclockwise-curving hodographs.