Meteorology
This domain tests altimetry, atmospheric stability, cloud and precipitation, fronts, thunderstorms, icing, wind shear, fog and local weather. Kenya-specific questions often involve the ITCZ, monsoon winds, orographic cloud and afternoon convection near Lake Victoria.
Altimetry
- QNH is the altimeter setting that shows elevation when on the ground; QFE shows height above the reference point; QNE is standard pressure 1013.25 hPa.
- Above transition altitude all aircraft use standard pressure; below it use the aerodrome QNH.
- 1 hPa ≈ 30 ft near sea level; flying from high to low pressure without resetting shows too high.
Weather systems
- Stable air gives layered cloud and steady precipitation; unstable air gives cumuliform cloud, showers and turbulence.
- A cold front can produce squall lines, wind shear and hail. Avoid embedded CBs.
- Icing risk is greatest in freezing rain and in cumuliform cloud between 0 and −20 °C.
Worked example
Surface temperature 24 °C, dew point 18 °C, spread 6 °C. Using the 400 ft per °C rule, convective cloud base is about 6 × 400 = 2,400 ft AGL. If the spread is small, expect low cloud and a greater fog risk.
Traps
- Setting QNE before the transition altitude.
- Confusing haze with fog: fog requires visibility below 1,000 m.
- Flying under a CB anvil, where hail and microbursts can occur.
- Assuming all tropical cloud is harmless; the ITCZ produces embedded CBs.
- Forgetting that temperature and dew point converge with cooling.