FAA Private Pilot Airplane (PAR)Weather Theory and ServicesMedium
A flight instructor asks a student what three conditions must be present for a thunderstorm to develop. Which combination correctly answers this question?
- AStable air, high humidity, and strong surface winds
- BA stationary front with no vertical motion
- CHigh pressure, subsidence, and dry air
- DSufficient water vapor, an unstable atmosphere, and a lifting mechanism
Show answer & explanationAnswer & explanation
Correct answer: D. Sufficient water vapor, an unstable atmosphere, and a lifting mechanism
Thunderstorm formation requires three ingredients: adequate moisture in the atmosphere, instability that allows air to keep rising once lifted, and a triggering (lifting) mechanism such as a front, convergence, or heating.
Why the other options are wrong
- A. Stable air resists vertical development, which is the opposite of what's needed.
- B. A lifting mechanism is needed, but stationary fronts alone don't guarantee moisture or instability, and 'no vertical motion' contradicts the requirement for lift.
- C. High pressure and subsidence suppress vertical development, preventing thunderstorms.
Thunderstorm Formation Requirements
Three ingredients must combine for thunderstorm development: sufficient moisture, an unstable air mass, and a source of lift.
- Moisture provides fuel for cloud/precipitation growth
- Instability allows continued upward parcel motion
- Lift can come from fronts, convergence, terrain, or heating
Memory trick: MIL: Moisture, Instability, Lift — like fueling, arming, and triggering a storm