Brownie pan convection. Fill a brownie pan with water. Light a candle and place it under the pan supported by inverted plastic cups. Move the candle to the center of the pan and let it heat up. There will be convection towards the candle on the bottom of the pan, up when over the candle, and away from the candle on the top surface. This may be visualized with a drop or drops of food coloring. Food coloring is denser than water and sinks to the bottom where it is drawn toward the candle, up and away on the top. If you are close, you can clearly see what is going on. This is very much like any strong storm or hurricane. The Coriolis force is not strong enough on these small scales to produce swirling seen in hurricanes. Using primary pigment colors allows discussion of color theory as well. I had elementary education students set this up and watch up close.
Brownie Pan Convection