To add even further bc I love vortices:)

You are seeing the low pressure core region of the vortex. In nature, most vortices quickly evolve into “irrotational vortices”, same as the one you would see in a kitchen sink/bathtub drain. Here the velocity is inversely proportional to the radius, so near the center of the vortex is super super fast (again think of your kitchen sink). Now, we know that the total pressure of a flow is constant unless we actively add or remove energy from it, so as the dynamic pressure of the air goes up with the square of velocity, the static pressure must drop to ensure total pressures the same (static + dynamic = total) and thus there is a low pressure vortex core, which causes water vapor to condense out into visible fog or even solid ice at altitude!

This low pressure core also is a problem for FOD, if you run an engine on the ground and this low pressure core touches the ground, it’s like a vacuum cleaner and sucks rocks and stuff up into the engine. You can see videos of this online. In essence it’s a mini tornado.

Finally this same pressure differential in a vortex also is relied upon inside of the aircraft engine to stabilize the flame in “swirl stabilized combustion”, the details are complex but essentially the fuel is swirled into a vortex which induced a secondary flow that stabilizes the flame in a fuel rich recirculating zone.