A few weeks ago I posted this great example of a water vortex in the form of a fountain. Here is another example from closer to home - from within a bath. As the water gets sucked out of the drain more water moves in to replace it. This water moves closer to the center and, in a simplified sense, has to move faster to conserve angular momentum. The same sorts of physics are involved in tornado creation although it is still unclear exactly how they form. Check out this artificial tornado from FYFD if you haven’t seen it already.
Credit:Dr. Rainer Kurz