The bear's cage is an informal chaser term for the tight zone of heavy rain, hail, and rotation that wraps around a supercell's low-level mesocyclone. It marks the area where a tornado can be hidden inside a curtain of precipitation, and where any close visual observation is at high risk.
Why the term exists
A mature supercell separates its updraft and downdrafts, but the low-level mesocyclone still sits inside a rotating cage of precipitation drawn around it by the storm's inflow and rear-flank downdraft. In classic supercells that curtain is thin enough to see through. In high-precipitation supercells it can be opaque.
The mental picture the name captures is a chaser standing near the bars of a cage while a hazard they cannot see clearly is on the other side. It is a slang term, not a formal category, but it maps to a real structural feature.
Where it forms and how chasers treat it
HP supercells are the archetype. Heavy precipitation wraps around the updraft base and closes off the visual read on the mesocyclone, which is why the NWS Norman glossary pairs its warning about the bear's cage with its advice that spotters keep a safe distance from any HP storm.
The standard chaser response is to stay well south of the hook echo and observe from a position where the storm is moving away, not toward the vehicle. Attempting to look up into the cage from the north or from the notch is where crews get overtaken by a tornado they never see.
How radar helps and where it fails
Dual-polarization radar has made rain-wrapped rotation easier to identify from a distance. A tight couplet in velocity, a debris signature in correlation coefficient, and a hook echo in reflectivity together give a strong picture of what is inside the cage. That picture is still limited by scan interval and by beam height at the observer's range.
None of those signatures gives a chaser sitting in the cage a real-time view of a nearby tornado. The bear's cage remains a place where radar tells the story and vision cannot.
Important limits
The term describes a region of risk, not a defined boundary. Its size and shape change with the storm's structure, precipitation loading, and motion. A chaser should treat any position where visibility is dropping toward the hook echo of a supercell as effectively inside the cage, regardless of whether the term is being used in real time.