FAA Flight Instructor Airplane (FIA)Weather and Weather ServicesMedium
A pilot planning an early-morning departure notes calm winds at the surface but a PIREP reports 40-knot winds at 2,000 feet AGL, just above a shallow surface-based temperature inversion. What hazard should the pilot anticipate during climb-out?
- ALow-level wind shear as the aircraft climbs through the inversion
- BClear air turbulence typical of jet stream crossings
- CCarburetor icing due to high humidity
- DFrontal thunderstorm activity along the inversion boundary
Show answer & explanationAnswer & explanation
Correct answer: A. Low-level wind shear as the aircraft climbs through the inversion
A strong wind speed and direction change concentrated in a shallow layer, such as across a nocturnal temperature inversion, is a classic setup for low-level wind shear, which can cause rapid airspeed and pitch changes during climb or descent through the layer.
Why the other options are wrong
- B. Clear air turbulence occurs at high altitude near jet streams, not near the surface.
- C. Carburetor icing is unrelated to wind shear across an inversion.
- D. No mention of thunderstorm activity is given in this scenario.
Low-Level Wind Shear (Inversion-Related)
A rapid change in wind speed and/or direction over a short vertical distance, often occurring at night when a temperature inversion traps calm surface winds beneath stronger winds aloft.
- Common on clear, calm nights with strong radiational cooling
- Can cause sudden airspeed loss or gain during climb/descent
- Often associated with a low-level nocturnal jet
Memory trick: Calm below, jet above the inversion — a shear sandwich.