Aviation Weather - Key Terms (Flashcards)

Flashcards covering wind shear, fog, thunderstorms, jet streams, mountain waves, radar and icing hazards, designed for aviation weather review.

Wind shear

A change in wind speed and/or direction with height; can occur at any atmospheric level and may be horizontal or vertical; often linked to wind shifts, speed gradients, inversions, frontal zones, or clear air turbulence near jet streams.

Low-level wind shear (LLWS)

Wind shear near the surface, typically encountered during takeoff and landing; commonly caused by thunderstorms, frontal activity, or low-level temperature inversions; can lead to sudden loss of airspeed and control.

Temperature inversion

A layer where temperature increases with height, which can trap shear and turbulence near the ground and contribute to LLWS.

Clear Air Turbulence (CAT)

Turbulence occurring in clear air, not associated with visible clouds; often found near jet streams and wind-shear zones, difficult to detect visually.

Thunderstorm

A storm with strong updrafts and often downdrafts; hazards include turbulence, wind shear, hail, and icing; life cycle includes cumulus, mature, and dissipating stages.

Cumulus stage

Thunderstorm stage dominated by vertical updrafts with little or no precipitation.

Mature stage

Thunderstorm stage with both strong updrafts and downdrafts and heavy precipitation; often the most intense part of the storm.

Dissipating stage

Thunderstorm stage where downdrafts dominate and the storm weakens and eventually dies out.

Squall line

A non-frontal, narrow band of active thunderstorms; often contains severe weather and poses significant hazards to aircraft.

Mountain waves

Airflow over mountains creates a wave pattern downwind, potentially causing severe turbulence, rotor clouds, and lenticular clouds.

Lenticular cloud

Lens-shaped cloud indicating standing waves in the lee of mountains; often a sign of possible strong turbulence in the area.

Rotor cloud

Rotating cloud forming in the lee of mountains near mountain waves; indicates hazardous rotor turbulence.

Advection fog

Fog formed when warm, moist air moves over a cooler surface (often coastal); can be persistent and spread inland.

Radiation fog

Fog formed by radiational cooling of the ground on clear, calm nights; tends to dissipate with surface warming or increasing wind.

Steam fog

Fog (sea smoke) formed when cold air moves over comparatively warm water; common in winter over seas or large bodies of water.

Hail

Precipitation in the form of hard ice pellets formed in thunderstorms; can be encountered away from the storm core and poses collision and damage hazards.

Tropopause

The boundary between the troposphere and the stratosphere, marked by an abrupt change in temperature lapse rate.

Jet stream

A narrow, fast-moving band of winds aloft; generally stronger in winter and can be farther south or north depending on the season; a major source of high-altitude wind shear and turbulence.

Low-Level Wind Shear Alert System (LLWAS)

Airport-based system that detects changes in wind speed and/or direction in the vicinity of an airport to warn of LLWS.

Advection fog dissipation threshold

Advection fog tends to lift when winds exceed about 15 knots; winds stronger than ~15 knots can lift fog into a low stratus layer.

Thunderstorm turbulence extent

Hazardous turbulence is present in thunderstorms; strongest within clouds; can extend tens of miles outside the cloud away from the storm core.

Radar echoes separation

To fly between very intense radar echoes, maintain a separation of at least 40 miles between the echoes.

Severe/intense echo avoidance distance

Thunderstorms identified as severe or giving intense radar echoes should be avoided by at least 20 miles, especially beneath the anvil.

Frost on wings

Frost on wings disturbs airflow and can cause premature separation and stall at a lower angle of attack, increasing takeoff stall risk.

Freezing precipitation

Rain or liquid precipitation that freezes upon contact or during descent when passing through subfreezing air; can result in freezing rain or ice pellets.

Anvil cloud

Flat, spreading top of a mature thunderstorm that signals the storm has reached the mature stage and may produce severe outflow and turbulence beneath.

Dust/haze as jet-stream cue

Visible dust or haze at flight level can help identify the jet stream and associated clear air turbulence (CAT) regions.