FAA Instrument Rating Airplane (IRA)Weather and Weather ServicesMedium
While flying beneath a large cumulonimbus cloud on a hot summer afternoon, a pilot observes streaks of precipitation extending from the cloud base that appear to evaporate before reaching the ground. What phenomenon is being observed, and what hazard may accompany it?
- AVirga, which can be associated with strong and unpredictable downdrafts including microbursts
- BAnvil crawler lightning, which poses a risk of electrical strikes to the aircraft
- CAdvection fog, which indicates increasing visibility restrictions at the surface
- DMammatus clouds, which typically indicate the storm has already dissipated
Show answer & explanationAnswer & explanation
Correct answer: A. Virga, which can be associated with strong and unpredictable downdrafts including microbursts
Virga is precipitation that evaporates before reaching the surface due to dry air beneath the cloud. The evaporative cooling process can create strong downdrafts, including microbursts, that pose a significant hazard to aircraft operating at low altitude near the storm.
Why the other options are wrong
- B. Anvil crawler lightning is a visible electrical discharge pattern, not a precipitation phenomenon.
- C. Advection fog forms from warm moist air over a cold surface, unrelated to precipitation streaks from clouds.
- D. Mammatus clouds are pouch-like formations on the underside of an anvil, not falling precipitation streaks.
Virga
Precipitation that evaporates before reaching the ground, often producing strong downdrafts due to evaporative cooling.
- Common under Cb clouds in dry low-level air
- Can produce microbursts and severe wind shear
- Visually appears as streaks hanging from cloud base
Memory trick: Virga vanishes, but the wind it leaves behind doesn't.