FAA Aircraft Dispatcher (ADX)MeteorologyHard
A dispatcher is evaluating an arrival airport report showing a strong low-level temperature inversion with a marked change in wind speed and direction between the surface and 2,000 feet. This scenario is most likely to produce which hazard on approach?
- ALow-level wind shear
- BOrographic turbulence
- CWidespread radiation fog
- DSteady-state icing conditions
Show answer & explanationAnswer & explanation
Correct answer: A. Low-level wind shear
A strong temperature inversion combined with a significant change in wind speed and/or direction with height creates the classic setup for low-level wind shear (LLWS), which can severely affect airspeed and aircraft performance during approach and landing. This hazard is commonly associated with nocturnal inversions, frontal passages, and thunderstorm outflows.
Why the other options are wrong
- B. Orographic turbulence is caused by terrain-forced airflow, not by a temperature inversion with wind shear.
- C. Radiation fog requires clear skies and calm winds, inconsistent with the strong wind shear described.
- D. Icing requires visible moisture and freezing temperatures, not specifically an inversion with wind shear.
Low-Level Wind Shear (LLWS)
A rapid change in wind speed and/or direction over a short distance near the surface, often caused by temperature inversions, frontal boundaries, or thunderstorm outflow, posing a hazard during takeoff and landing.
- Commonly caused by nocturnal temperature inversions with strong wind gradients aloft
- Also caused by thunderstorm gust fronts/microbursts and frontal passages
- Detected using LLWAS (Low-Level Wind Shear Alert System) at equipped airports
Memory trick: 'Inversion + wind change = Shear on approach, watch your airspeed disappear!'