FAA Instrument Flight Instructor (FII)WeatherMedium
During a cross-country flight, a pilot reports towering cumulus clouds, a bumpy ride, and unlimited visibility except in isolated rain showers. This report is most indicative of which air mass characteristic?
- AInversion layer air mass
- BStable air mass
- CUnstable air mass
- DSaturated stable air mass
Show answer & explanationAnswer & explanation
Correct answer: C. Unstable air mass
Unstable air produces good visibility (except in showers), cumuliform clouds with vertical development, turbulent conditions, and showery precipitation—all present in this report. Stable air typically produces stratiform clouds, smooth flying, poor visibility due to haze, and steady precipitation.
Why the other options are wrong
- A. An inversion layer promotes stability and stratiform clouds, not the described conditions.
- B. Stable air produces smooth rides and stratiform clouds, not towering cumulus and turbulence.
- D. Stable air does not typically produce vertical cloud development like towering cumulus.
Unstable Air Mass Characteristics
Unstable air rises freely, producing cumuliform clouds, turbulence, showery precipitation, and good visibility except in precipitation.
- Cumuliform clouds with vertical development
- Turbulent, bumpy flying conditions
- Good visibility except in showers
Memory trick: Unstable air 'Ups and Bumps'—towering clouds and turbulence.