thunderclaps

Thunderclaps are the audible component of a lightning discharge during a thunderstorm. The term describes the sharp crack or explosive clap heard near the bolt and the subsequent acoustic phenomena produced as sound waves propagate through the atmosphere. Depending on distance and atmospheric conditions, thunder can appear as a sudden, bright crack or as a longer, rolling rumble that lasts several seconds.

Mechanism: Lightning rapidly heats surrounding air to extreme temperatures, causing rapid expansion and the formation of a shock wave. That shock wave travels through the air as sound, which is perceived as thunder. Close-scale discharges tend to produce a brief, piercing crack, whereas more distant lightning can yield a prolonged, resonant rumble. The exact sound depends on the lightning channel geometry, wind aloft, temperature gradients, and humidity.

Perception and distance: The intensity and character of a thunderclap are influenced by atmospheric conditions and the observer’s distance from the lightning. Sound can be muffled or refracted by wind, temperature inversions, and humidity, affecting how loud or prolonged it seems. The time delay between the visible flash and the thunder’s arrival provides a rough estimate of distance, with about three seconds per kilometer as a common rule of thumb.

Occurrence and usage: Thunderclaps occur only during thunderstorms when electrical discharges occur within or between clouds and the ground. In broader usage, the phrase thunderclap can describe a sudden, dramatic event or realization, used metaphorically to denote a startling or impactful moment.