A cloud-to-ground lightning stroke develops in three stages: first, an unstable atmosphere with warm air at the ground and cooler air in clouds leads to charge separation within thunderstorm clouds, with negative charge accumulating at the top and positive at the bottom; second, this charge buildup destabilizes the atmosphere; third, when the charge imbalance is great enough, a lightning stroke connects the cloud and ground charges.

1. How a Cloud-to-Ground
Lightning Stroke Develops

2. Destabilization of Atmosphere
• Unstable atmosphere=
thunderstorm
– Warm air on ground
– Cloud air above
• Cloud charge:
– Negative top
– Positive bottom

3. Stages of Development