Rear flank downdraft, also known as RFD is one of the more violent areas of a supercell thunderstorm and often makes the difference between a safe chase and a dangerous chase. Rearflank Downdrafts come in two forms, low precipitation and high precipitation. High precipitation rear flank downdrafts mean there is a high precipitation supercell and should be avoided by tornado chasers as the tornado often becomes rain wrapped, and you may end up driving right into it.
On radar rear flank downdrafts can be identified by the hook echo, and in person they can be identified by the clear slot next to them. For more on how to identify rear flank downdraft check out this video by the Tornado Titans.
Photo Courtesy of the National Weather Service
