Thunderstorms, Icing, Turbulence and Other Aviation Hazards
Thunderstorms
A thunderstorm requires three ingredients: sufficient moisture, conditional instability and a lifting trigger. Stages are cumulus (updrafts), mature (updrafts, downdrafts, rain, lightning, hail, gust front) and dissipating (downdrafts dominate). Hazards include severe turbulence, hail, lightning, microbursts, wind shear, icing and tornadoes. Never fly beneath a storm; avoid by at least 20 nm where possible, and never attempt to overfly a cumulonimbus.
Icing
Structural icing occurs in supercooled water droplets. Types: clear (rime-free, large droplets, strong lift, spreads back), rime (small droplets, rough, builds forward), and mixed. Greatest risk is typically between 0°C and −15°C in stratiform or cumuliform cloud. Hazards: loss of lift, increased weight and drag, blocked pitot/static, carburettor icing (which can occur at outside temperatures up to 20°C with high humidity).
Turbulence and wind shear
Turbulence types include convective, mechanical (terrain/obstacles), frontal, clear-air (CAT, near jet streams) and wake turbulence. Low-level wind shear and microbursts are critical near the ground; go-around is the correct response.
Traps
Questions confuse clear and rime ice formation conditions, or underestimate carburettor icing. Others forget that CAT occurs in clear air near jet streams.
Rule of thumb
Avoid cumulonimbus by 20 nm laterally and never overfly; expect the strongest icing between 0°C and −15°C; treat any microburst alert as a go-around.