Thunderstorm hazards
Thunderstorms are the most dangerous weather phenomenon for aviation — concentrating several extreme hazards in one cloud.
Source: FAA AC 00-6B; WMO; ICAO Doc 9817.
Main hazards
| Hazard | Effect |
|---|---|
| Severe turbulence | Structural stress, injury risk |
| Hail | Windshield damage, paint, sensor failures |
| Lightning | Avionics failure, magnetic-compass damage, structural damage, crew dazzle |
| Microburst / wind shear | Life-threatening altitude loss on take-off/approach |
| Severe icing | Cb with SLD character |
| Precipitation | Loss of visibility, aquaplaning |
| Tornado | In supercells — total aircraft destruction |
Cb of great vertical extent
Cumulonimbus (Cb) clouds with great vertical extent often feature no flight visibility, severe turbulence, severe icing at temperatures around or below freezing, and electrical discharge due to intense convective activity and supercooled water droplets.
Underflying a Cb — danger
When underflying a cumulonimbus (Cb) cloud in anticipated thunderstorm conditions, even with initially good visibility and sufficient cloud base, pilots must especially anticipate sudden onset of heavy rain, hail, turbulence, and lightning due to the cloud's intense convective activity.
Roll cloud — ahead of the storm
Roll clouds can run ahead of a thunderstorm with a maximum distance of about 20 km:
- Cold air rushing down from a Cb with precipitation causes the formation of a roll cloud.
- Indicator of outflow → strong wind shear, microburst risk.
Dangerous phenomena outside precipitation
Dangerous weather phenomena can also occur outside of thunderstorm precipitation close to the ground. These are gusts and turbulence:
- Outflow boundary 20-50 km from the Cb.
- Microburst possible in apparently harmless weather.
Lightning effects (recap Subject 060)
- Crew dazzle.
- Avionics interference.
- Mechanical damage.
- Magnetic compass permanently mismagnetised.