FAA Instrument Flight Instructor (FII)WeatherMedium
During a weather briefing, a pilot learns that a fast-moving cold front is overtaking a slower warm front ahead of it along the route of flight. This process forms which type of front, and what weather should the pilot expect near the point of occlusion?
- AA stationary front, with little cloud or precipitation activity
- BA squall line forming well ahead of the warm front with severe turbulence but no precipitation
- CAn occluded front, with weather that can combine characteristics of both frontal types and possible embedded thunderstorms
- DA dry line, with a sharp moisture gradient but minimal cloud cover
Show answer & explanationAnswer & explanation
Correct answer: C. An occluded front, with weather that can combine characteristics of both frontal types and possible embedded thunderstorms
When a faster cold front catches up to a slower warm front, the warm air is lifted completely off the surface, forming an occluded front. Weather near the occlusion can be complex and severe, combining cold-front-type showers/thunderstorms with warm-front-type stratiform clouds and precipitation.
Why the other options are wrong
- A. A stationary front forms when neither air mass advances, not when one front overtakes another.
- B. Squall lines can precede cold fronts but are not the result of frontal overtaking described here.
- D. A dry line is a moisture boundary, unrelated to a cold front overtaking a warm front.
Occluded Front
An occluded front forms when a fast-moving cold front overtakes a slower warm front, lifting the warm air mass completely off the ground and combining both frontal weather characteristics.
- Cold front catches up to warm front
- Warm air mass lifted aloft
- Weather can include both stratiform and convective elements
- May produce severe, embedded thunderstorms
Memory trick: Occlusion = a cold front sneaking up and squeezing the warm front off the ground