A topic in the Open Knowledge Graph — a free, open map of 15,290 topics and the order to learn them in.
Thunderstorms develop in three stages — cumulus (development), mature (full convective cell with updrafts, downdrafts, lightning, and heavy precipitation), and dissipating (downdrafts dominate, cutting off moisture supply). Convective Available Potential Energy (CAPE) measures atmospheric instability — the energy available to a rising air parcel. Charge separation in cumulonimbus clouds occurs as ice crystals and graupel interact in the mixed-phase region near -10 to -25°C, creating a positive charge in the upper anvil and negative charge in the mid-levels. Lightning is a rapid discharge neutralizing this separation; thunder is the acoustic shock wave from the rapid heating of the lightning channel to ~30,000 K.
Work through a sounding (atmospheric profile plot) to identify the level of free convection, equilibrium level, and CAPE. Distinguish ordinary single-cell storms from multi-cell and supercell thunderstorms, noting which conditions produce each.
A thunderstorm is an atmospheric heat engine that converts the potential energy stored in warm, moist air into the kinetic energy of violent updrafts and downdrafts. The fuel for this engine is latent heat — the energy released when water vapor condenses into liquid droplets and when droplets freeze into ice. From your study of cloud formation, you know that rising air cools adiabatically and eventually reaches its dew point, forming a cloud. In an unstable atmosphere, the latent heat released by condensation warms the rising parcel, making it even more buoyant than its surroundings, so it continues accelerating upward. This positive feedback is what distinguishes a towering cumulonimbus from an ordinary fair-weather cumulus.
The life cycle of a single-cell thunderstorm follows three distinct stages. In the cumulus stage, a strong updraft (often 10–30 m/s) dominates the cell, carrying moisture upward and building the cloud vertically. There is no rain yet because the updraft suspends all precipitation particles aloft. The mature stage begins when precipitation particles grow too heavy for the updraft to support — rain and hail begin falling, dragging air downward and creating a downdraft alongside the existing updraft. This stage produces the storm's most intense weather: heavy rain, lightning, strong surface winds from the spreading downdraft (called a gust front), and possibly hail. The dissipating stage arrives when the downdraft spreads across the surface and cuts off the warm, moist inflow that feeds the updraft. Without fuel, the updraft collapses, precipitation weakens, and the storm dies — typically within 30–60 minutes for a single cell.
Lightning results from charge separation within the cumulonimbus cloud. In the mixed-phase region (roughly −10°C to −25°C), collisions between small ice crystals rising in the updraft and larger graupel (soft hail) falling through it transfer charge: ice crystals carry positive charge upward to the anvil, while graupel accumulates negative charge in the mid-levels. This creates an enormous electric potential difference — hundreds of millions of volts — between the upper and lower portions of the cloud, and between the cloud base and the ground. When the electric field exceeds the air's dielectric breakdown threshold (about 3 million V/m in dry air, less in moist conditions), a stepped leader — a jagged, branching channel of ionized air — propagates downward. When it nears the ground, an upward return stroke surges through the channel at a third the speed of light, heating the air to roughly 30,000 K and producing the brilliant flash. The explosive expansion of this superheated channel creates a shock wave that we hear as thunder. Because light travels almost instantaneously while sound moves at roughly 340 m/s, counting the seconds between flash and rumble gives you the storm's distance — about one kilometer for every three seconds of delay.