FAA Flight Instructor Airplane (FIA)Weather and Weather ServicesMedium
During a cross-country flight planning briefing, a flight instructor explains the polar front jet stream to a student. Which statement best describes this feature?
- AIt is a narrow band of strong winds near the tropopause associated with a strong temperature gradient between air masses
- BIt forms exclusively in the tropics along the intertropical convergence zone
- CIt is a stationary belt of calm winds separating high and low pressure systems
- DIt is a low-level nocturnal wind maximum found only over flat terrain
Show answer & explanationAnswer & explanation
Correct answer: A. It is a narrow band of strong winds near the tropopause associated with a strong temperature gradient between air masses
The polar front jet stream is a relatively narrow, fast-moving river of air found near the tropopause where a strong horizontal temperature gradient exists between polar and tropical air masses; wind speeds can exceed 150-200 knots, especially in winter.
Why the other options are wrong
- B. This describes tropical easterly features, not the polar front jet.
- C. Jet streams are fast-moving, not calm or stationary.
- D. This describes a low-level nocturnal jet, a different phenomenon.
Polar Front Jet Stream
A narrow band of strong westerly winds located near the tropopause, formed by the temperature contrast between polar and tropical air masses.
- Typically found between 30,000-40,000 feet MSL
- Wind speeds can exceed 200 knots in winter
- Associated with clear air turbulence (CAT) near its core
Memory trick: Jet stream: a river of wind riding the temperature cliff.