FAA Airline Transport Pilot (ATM)Meteorology and Weather ServicesMedium
A flight planner is evaluating winds aloft for a high-altitude transcontinental flight and wants to identify the region most likely to produce clear air turbulence associated with the jet stream. Where should this be expected?
- AIn the stratosphere above 60,000 feet, unrelated to any temperature contrasts
- BAt the base of cumulonimbus clouds, generally near 10,000 feet
- CNear the surface, along frontal boundaries below 5,000 feet
- DNear the tropopause, typically between 30,000 and 40,000 feet, along boundaries of contrasting air masses
Show answer & explanationAnswer & explanation
Correct answer: D. Near the tropopause, typically between 30,000 and 40,000 feet, along boundaries of contrasting air masses
The jet stream is a narrow band of strong winds located near the tropopause, typically 30,000-40,000 feet, forming where air masses with sharp temperature contrasts meet. The strong wind shear associated with the jet stream's core is the primary cause of clear air turbulence (CAT) at these altitudes.
Why the other options are wrong
- A. The jet stream is found near the tropopause, not high in the stratosphere.
- B. Turbulence near cumulonimbus bases is convective, unrelated to jet stream shear.
- C. Surface-level frontal turbulence is mechanical/frontal, not related to the jet stream.
Jet Stream and CAT
A narrow band of strong upper-level winds near the tropopause, formed by strong temperature gradients between air masses; associated with clear air turbulence from wind shear.
- Typically found 30,000-40,000 ft altitude
- Wind speeds can exceed 100 knots in the core
- CAT is strongest on the low-pressure (poleward) side of the jet core
Memory trick: Jet stream = the sky's 'highway,' bumpy where lanes of air merge.