A thunderstorm with

• straight-line winds gusting to 57 mph (50 knots) or more
  and/or
• hail 3/4" in diameter (quarter-sized) or larger
  and/or
• tornadoes

The definition was made to highlight thunderstorms liable to pose an enhanced hazard to life and property.

Two other phenomena associated with thunderstorms also cause a hazard to life and property and are NOT included in this definition.

What are they and why do you think they are not included?