A pilot can expect a wind shear zone in a temperature inversion whenever the windspeed at 2,000 to 4,000 feet above the surface is at least

• A. 15 knots
• B. 25 knots
• C. 35 knots
• D. 50 knots

Answer: (B)

Wind shear is a rapid change in wind speed or direction over a short vertical distance. In a temperature inversion, the air below the inversion is stably layered and mixing is suppressed, so the wind tends to increase with height, creating a sharp gradient at the inversion boundary. When the wind speed at 2,000 to 4,000 feet above the surface reaches about 25 knots or more, this gradient becomes strong enough to form a noticeable wind-shear zone in the inversion. That abrupt change can affect lift and airspeed as you move through the layer, which is especially important during takeoff, approach, or low-altitude flight.

Choices with lower wind speeds (like 15 knots) are generally not enough to produce a pronounced shear in the inversion, while much higher speeds (35 or 50 knots) represent stronger-than-typical conditions; the standard expectation for encountering a wind-shear zone in a temperature inversion is around 25 knots, making that the best answer.