Legend Storm-relative Helicitity (SRH) in m²/s² = colors Bunkers Storm Motion in knots = wind barbs SRH is a measure of rotation potential. Some critical values SRH: If showers form: 150-300: supercell development possible with large CAPE, risk for weak tornadoes (F0, F1) 300-450: supercell development possible with small CAPE, risk for strong tornadoes (F2, F3) >450      : large risk for supercell development, risk for violent tornadoes (F4, F5)  Bunkers Storm Motion barbs determines the movement of supercells. Barbs indicate direction and speed. Wind speed is indicated in knots. Wind barbs always point in the direction the wind is blowing "from". A short barb means 5 knots, a long barb means 10 knots. (check:  wind speed converter)    In the above example the orientation of the wind barb indicates winds from the northeast with a speed of 15 knots.