Final answer:
Supercell tornadoes typically form at the intersection of the updraft and the rear flank downdraft within a supercell thunderstorm, resulting from a vertically tilted rotating column of air.
Step-by-step explanation:
Supercell tornadoes are observed to form at the boundary between the updraft and rear flank downdraft (RFD) within a supercell thunderstorm. Initially arising from a horizontally rotating column of air induced by wind shear, these columns are tilted into a vertical position by updrafts. The supercell's mesocyclone, a deep, persistently rotating updraft, plays a crucial role in the tornado's formation.
When conditions are favorable, the interaction between the updraft and the surrounding downdrafts can lead to the intensification of rotation at lower altitudes, eventually creating a tornado. Often, this takes place near the rear flank downdraft where it wraps around or cuts under the updraft. This can be an area of intense wind shear, which can further enhance the rotation and contribute to the development of a tornado. Notably, these powerful tornadoes can reach speeds up to 500 km/h, as observed in phenomena descending from clouds with a violent, funnel-like appearance.