FAA Aircraft Dispatcher (ADX)MeteorologyHard
An LLWAS (Low-Level Wind Shear Alert System) sensor array at an airport detects a sudden 45-knot wind shift and a strong divergence pattern across a very localized area near the runway threshold, lasting only about 8 minutes. This signature is most characteristic of which hazard?
- AA microburst
- BA gust front from a distant thunderstorm
- CMountain wave rotor turbulence
- DA dust devil
Show answer & explanationAnswer & explanation
Correct answer: A. A microburst
A microburst produces an intense, localized downdraft that spreads out upon reaching the surface, creating a divergent wind pattern with rapid, extreme changes in wind speed and direction over a very small area (typically less than 2.5 miles across) and a short duration (usually 5-15 minutes). This matches the localized divergence and brief duration described.
Why the other options are wrong
- B. A gust front is typically broader in scale and associated with the leading edge of outflow from a larger storm system, not a tight localized divergence.
- C. Mountain wave rotor turbulence occurs on the lee side of mountains and is tied to terrain-induced waves, not a localized divergent outflow.
- D. Dust devils are small-scale, dry convective vortices typically weaker and not detected as a divergent shear event by LLWAS.
Microburst
A small-scale, intense downdraft that spreads out horizontally upon hitting the ground, producing rapid and severe changes in wind speed and direction over a very short time and distance.
- Diameter typically less than 2.5 nautical miles
- Lifespan usually 5-15 minutes
- Can produce headwind-to-tailwind shear exceeding 45 knots, extremely hazardous on approach/departure
Memory trick: Microburst = a bucket of air dumped straight down, splashing outward fast and hard.