Severe Weather: Thunderstorms, Lightning, and Tornadoes

Comprehensive vocabulary flashcards covering the characteristics, life cycle, forms, and atmospheric dynamics of thunderstorms, lightning, and tornadoes.

Thunderstorm (T-storm)

A cumulus cloud that produces lightning and thunder, typically lasting $1\text{ - }3\text{ hours}$ on average (up to $12\text{ hours}$ or more), signaling great atmospheric instability and strong vertical development.

Cumulus Stage

The initial build-up stage of a thunderstorm fueled by updrafts of warm, moist air (moving up to $160\,\text{kph}$) cooling adiabatically.

Entrainment

An influx of cool, dry surrounding air into a developing thunderstorm that helps fuel downdrafts.

Mature Stage

The stage of a thunderstorm in which falling raindrops initiate downdrafts fueled by entrainment, producing heavy rains.

Dissipating Stage

The final stage of a thunderstorm occurring as the rate and amount of rain decrease due to the loss of warm, moist air and latent heat energy, causing the cloud mass to break up and evaporate.

Derecho

A strong linear or "straight-line" wind event occurring when winds exceed $58\,\text{mph}$, capable of exceeding $100\,\text{mph}$ (record $128\,\text{mph}$), primarily between May and August in the Upper Midwest.

Microburst

A small, severe downburst less than $2\,\text{mi}$ in diameter produced by a thunderstorm, generating wind shear capable of damaging or crashing aircraft.

Step Leader

An invisible pathway of charges established from the cloud base toward the ground, forming the initial step of a cloud-to-ground lightning strike.

Return Stroke

The movement of opposite charges back cloudward once a pathway reaches the ground, illuminating the channels and creating the visible flash of lightning.

Ball Lightning

A type of lightning that appears as a round, glowing mass of electrified air, typically basketball-sized or smaller and lasting around $15\,\text{seconds}$.

St. Elmo’s Fire

A luminous electrical discharge phenomenon resulting from ionization.

Sprites

Large, short-lived electrical phenomena that look like giant red jellyfish and can reach up to $57\,\text{miles}$ above thunderstorm cloud tops.

Blue Jets

An upward-moving electrical ejection traveling at about $60\,\text{mph}$ and reaching heights of $30\,\text{miles}$ above the Earth's surface.

Thunder

The sound emitted when a lightning flash heats surrounding air to between $15{,}000^\circ\text{C}$ and $33{,}000^\circ\text{C}$ in milliseconds; it travels at approximately $1082\,\text{feet/sec}$ (speed of sound), taking about $5\,\text{seconds}$ to cover $1\,\text{mile}$.

Tornado

A violently rotating column of air extending downward from a cumulonimbus cloud in response to extremely low air pressure, where central barometric pressure can be $90\text{ - }100\,\text{mb}$ below the surrounding air.

Enhanced Fujita Scale

A modified scale based on the work of Dr. Ted Fujita used to measure tornado wind speeds, ranging from EF0 ($65\text{ - }85\,\text{mph}$) to EF5 ($> 200\,\text{mph}$).

Mesocyclone

A rotating column of air created when near-ground air rolls horizontally due to friction and vertical speed differences, which is subsequently drawn upward into a thunderstorm to produce stronger tornadoes ($\text{EF3}$ to $\text{EF5}$).