A cyclic supercell is a long-lived supercell that repeatedly develops a low-level mesocyclone, occludes it, and organizes a new one on the same storm, producing a series of mesocyclones in sequence over the storm's lifetime. Each cycle can produce its own tornado, so a single cyclic storm may generate several tornadoes over the course of a few hours.
The cycle in physical terms
A cyclic supercell alternates between two phases. In the tornadic phase, a low-level mesocyclone is fed by warm, moist inflow and stretched vertically by a strong updraft, and a tornado can form beneath it. In the occlusion phase, the storm's own rear-flank downdraft wraps around the meso, cuts it off from the warm inflow, and weakens it.
Once the old meso occludes, the leading edge of the wrapped outflow acts as a new source of convergence and lift downshear from the previous circulation. Warm inflow rising along that new boundary builds a fresh updraft, a new low-level mesocyclone organizes inside it, and the tornadic phase begins again. Numerical simulations by Adlerman, Droegemeier, and Davies-Jones showed this behavior repeating on timescales of roughly 20 to 60 minutes per cycle.
What favors cycling
Not every supercell cycles. The behavior is more common when the environment supports a strong low-level updraft that can quickly rebuild after each occlusion, when storm-relative inflow remains warm enough to continue feeding new mesos, and when the storm keeps encountering fresh, unmodified air along its motion.
Deep-layer shear, storm-relative helicity, and a low LCL all appear to help. Boundary interactions can also trigger renewed cycling. A storm that meets an outflow boundary or a warm front can generate a new low-level meso along the intersection almost immediately after the previous one occludes.
How chasers and forecasters use it
Recognizing a cyclic supercell in progress changes the reading of a storm's radar and visual signatures. A shrinking, rope-stage tornado near the back edge of the storm is not the end of the day. A forecaster or chaser watches for a new wall cloud building along the flanking line to the south or southeast, and for the mid-level rotation to shift with it.
Warning meteorologists extend their attention downshear when a storm enters an occlusion phase, because that is where the next tornado is most likely to form. Tracking cycle timing across the first two cycles often gives a rough estimate of when the third will occur, useful for staging warnings and spotter positioning.
Where the label misleads
Cyclic behavior is a tendency, not a guarantee. A storm that produces one tornado and occludes may simply run out of inflow, drift into a cooler airmass, or lose organization to a merging cell rather than starting a new cycle. Assuming every long-lived supercell will keep cycling can lead to over-warning downshear.
The label also gets stretched. A storm that produces a family of tornadoes from separate mesocyclones is cyclic. A storm that produces a single tornado over a long track from one persistent meso is not, even if the tornado is destructive. Both patterns exist, and distinguishing them matters for how the storm is described in real time and in the survey record.