Fronts and air masses
Cold fronts move quickly and produce narrow bands of vigorous convection. Warm fronts bring extensive stratiform cloud, steady precipitation and long stretches of IMC. Occlusions combine the worst of both.
Jet streams and turbulence
Jet cores can exceed 200 kt. Strong shear on their flanks generates clear-air turbulence, which no radar can see. Planners use forecast shear charts rather than eyesight to avoid it.
Icing and thunderstorms
Structural icing is worst between 0 and −20°C in visible moisture, with supercooled large droplets the most dangerous case. Thunderstorms should be avoided by 20 nm laterally, and overflying the anvil is not a safe strategy.
Key points
- Cold fronts: narrow, violent. Warm fronts: broad, persistent IMC.
- Clear-air turbulence is invisible to weather radar.
- Avoid convective cells by at least 20 nm, especially downwind.
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