Air Masses, Fronts and Synoptic Weather Systems
Air masses
Air masses take the characteristics of their source region: continental (dry) or maritime (moist), tropical (warm) or polar (cold). Classifications include mT, cP, mP, cT. When they move, they bring their temperature and moisture to new areas and modify the weather there.
Fronts
A cold front has a steep slope (roughly 1:50), fast movement, narrow band of heavy showers, thunderstorms, squall lines, rapid wind shifts and a sharp temperature drop after passage; visibility improves behind. A warm front has a shallow slope (roughly 1:150), slow movement, a wide belt of layered cloud (cirrus → cirrostratus → altostratus → nimbostratus) and steady rain ahead, with a gradual temperature rise. An occluded front forms when a cold front overtakes a warm front; a stationary front shows little movement. A trough is a line of low pressure with convective weather; a ridge brings fine weather.
Synoptic systems
Depressions (low pressure) rotate counterclockwise in the Northern Hemisphere, converge and rise, producing cloud and rain. Anticyclones subside, giving clear, stable weather. Candidates must read isobar spacing for wind strength and identify frontal symbols.
Traps
Questions reverse the slope or the cloud sequence of warm fronts, or claim cold fronts bring prolonged steady rain. Remember that warm-front cloud arrives well ahead of the surface front.
Worked example
A pilot sees cirrus, then lowering altostratus and steady rain over several hours - a warm front approaching. Expect a gradual wind veer, falling pressure and a slow temperature rise after passage.