No Wind

On the way to New Haven the other day, when driving through Bridgeport, Connecticut, I spied this unusual cloud of smoke in the sky.  This is the coal-fired United Illuminating plant on the harbor in Bridgeport.  So I started thinking about what might cause this, and realized that there was not a hint of wind blowing, so the smoke was rising straight up from the red and white striped stack.  I don't remember ever seeing this before. It makes for an interesting shape in the sky.