Type 3 RFD surge (at right), in which the low-level mesocyclone is initially ahead of the RFD boundary. The RFD boundary surges toward the supercell’s forward flank, and to the center of the low-level mesocyclone. An RFD occlusion forms on the RFD boundary, underneath the low-level mesocyclone. The tornado develops within the RFD occlusion, on the RFD boundary, eventually moving southwestward into the RFD. For the Ravanna, Kansas EF3 tornado on May 24, 2016 (at right), the mesocyclone was initially to the east of the RFD boundary. The RFD surge was instigated by outflow associated with cell mergers west of the boundary (panel 2). As the RFD surged toward the forward flank, the RFD occlusion developed on the RFD boundary (panel 2 and 3). Then, the tornado formed in the RFD occlusion (panel 4). 300 meter ground-relative flow is estimated based on cell movement and outflow.