Chasing techniques#supercell#tornado
RFD — Rear-Flank Downdraft
Also: RFD
At a glance
The clear slot that wraps around the back of a supercell's updraft. Critical for tornado genesis — and dangerous if you're standing in the wrong place when it arrives.
Deep dive
The RFD is a mesoscale downdraft that descends behind and under a supercell's mesocyclone, curling cyclonically around it. It's tied to tornadogenesis because its gust front (the RFD surge) tightens the low-level rotation by convergence.
Observationally: a clear slot opens on the rear-right of the storm, a wall cloud lowers, and surface temperatures drop with a wind shift. A cool RFD (strong temperature deficit) is actually a bad tornado signal — it under-cuts the mesocyclone. A warm RFD (small deficit) is pro-tornadic.