The central part of the disc thus formed soon disappears, and consequently a ring form results. This is a very slowly whirling vortex ring. As it proceeds, the radius of the ring is augmented ...

"This process acts in tenths of a second, so the ring is emitted impulsively into the air domain. Due to its own momentum, thermal buoyancy and to the inertia of the rotating fluid, the vortex ...

The easy answer is a deep southward dip in the polar jet stream that typically rings the globe at higher ... Is this stream ...