New answers tagged vortex
Because where they come close together the air in between circulates in such a way as to join them in a single path. Floris is right, but maybe this picture helps.
Intuitive start of an answer: If you have counter rotating vortices they have zero net angular momentum (to first order). If they merged they would have to have no motion -> where did the energy go. In between the two axes of rotation the fluid moves in the same direction and has no mechanism for dissipation. By contrast for two vortices with the same ...
It's the radial motion of low-density air being drawn into the upflow. Angular momentum is conserved, so as the radius decreases the angular velocity increases. For weather systems, the original angular momentum comes from the Earth's rotation.
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