A thunderstorm cell has reached the mature stage of its life cycle. What is the key signal that this stage has begun?

Why: The Remote Pilot Study Guide identifies the start of the mature stage this way: "Precipitation beginning to fall from the cloud base is your signal that a downdraft has developed and a cell has entered the mature stage." Updrafts and downdrafts in close proximity during this stage create strong vertical shear, and all thunderstorm hazards reach their greatest intensity during the mature stage.

• Describes the opposite of the mature stage, which is the most hazardous and turbulent phase of the thunderstorm life cycle, not a period when turbulence ceases.
• Describes the dissipating stage, the third and final phase after downdrafts have abated — not the mature stage, which the question asks about.