Your explanation is correct, except that the Coriolis effect does not control the rotational direction in a flushing toilet. The Coriolis effect is tiny and takes a long time (at least several hours) to exhibit any detectable influence on fluid motion. The time scale of a tropical cyclone is long enough (days going into weeks), but a toilet flush happens too rapidly (within seconds) to be modified by the rotation of the earth. The rotational direction in a toilet is governed by the direction of the water inlets around the rim. I've seen a video of a very careful experiment done to demonstrate this - a round tank 8-10 feet in diameter drained slowly through a small outlet (an inch or less), and it took many hours to observe the Coriolis effect. I'm sure of this because I was asked it during my qualifiers - at that time toilet rotation had recently been spoofed in a Simpsons episode set in Australia: the American embassy had special pumps installed to force their toilets to flush in the northern hemisphere direction - very funny, it was.
... if it takes a minimum of several hours for the Coriolis force to have any influence, why do nearly 100-percent of tornadoes rotate counterclockwise? In that case, the rotation can become established in a manner of minutes, yet nearly all of them spin in the "expected" direction. You'd think that if the Coriolis effect weren't at work, tornadoes spinning clockwise would be a common occurrence.
I'm not disagreeing with you, just "wondering" if you know about that.
But a mantra like that sure would help sell a lot of shiny new sophisticated boats to new paddlers. Let’s spread it around. The industry could use a lift.
Long process Well, tornadoes are generally produced within large storm systems that would already be rotating CCW as expected, so when the local intensification happens that produces the tornado itself, the general circulation is already well established. The tornado is a focused part of a larger system that took time to form.
Re: the remark below, as most tornadoes turn CCW, there are situations where multiple CCW tornadoes in proximity will rotate about each other (due to the induced motion of one upon the other) while they are progressing across the landscape. CW tornadoes can get spun off from big CCW tornadoes, but are primarily a by-product. Tornadoes of opposite rotation will also rotate about each other, or if they are the same strength (not expected) move as a pair in a straight line. I believe big tornadoes have been observed splitting into multiples and multiples can merge, but I may be remembering the results of storm simulations rather than actual observations.