A chronograph is a watch that can be used to measure elapsed time. It typically has a start/stop button and a reset button. When the start/stop button is pressed, the chronograph begins to measure elapsed time. When the start/stop button is pressed again, the chronograph stops measuring elapsed time and the time that has elapsed since the start/stop button was first pressed is displayed. The reset button can be used to reset the chronograph to zero.
A tempest is a violent storm.