The answers by McD and idg have been very direct and to the point . I would just like to expand...although deviating from the direct answer.
Very heavy rain can give echoes even at 180 nm range. Such returns could give severe turbulence at 18000-30000 ft. However in monsoon conditions you may get " red " returns without any turbulence at lower altitudes. The storm cells can also be further examined by using tilt and gain to get a three dimensional view. However that is not required if you have the magenta with doppler sensor for turbulence detection. This actually detects the gradient and stronger the gradient more severe the turbulence !!
I hope that was useful.. Regds and HAPPY LANDINGS!!!!!
