Meteorology
Meteorology tests reading the sky and the paperwork: METAR and TAF decoding, pressure and altimetry, stability and cloud, fog, icing, thunderstorms, wind shear, and regional weather such as shamal dust episodes and coastal or inland fog in the UAE.
Reports and codes
- METAR gives wind in degrees magnetic and knots, visibility in metres, weather, cloud amount and height in hundreds of feet AGL, temperature and dewpoint in °C, and QNH in hPa.
- CAVOK means 10 km or more visibility, no cloud below 5,000 ft or the minimum sector altitude, and no significant weather; 9999 means 10 km or more.
- Trend groups: BECMG indicates a gradual permanent change, TEMPO a temporary fluctuation.
Pressure and altimetry
- QNH gives altitude above mean sea level, QFE gives height above the aerodrome reference point, and 1013.2 hPa gives flight levels.
- Near the surface, 1 hPa is about 27 ft; a 4 hPa error is roughly 108 ft of height error.
Cloud, fog and local weather
- Convective cloud base in feet AGL is approximately (temperature − dewpoint) × 400.
- Radiation fog needs a clear sky, light wind and high relative humidity, typically around dawn in winter; advection fog forms when warm moist air moves over a colder surface.
- In the UAE a shamal brings strong north-westerly winds with dust and haze and a sharp visibility reduction; summer afternoons produce convection over the Hajar mountains and a coastal sea breeze, and winter mornings can bring radiation fog at inland and coastal airports.
Worked example
OMDB 121200Z 30012KT 5000 HZ NSC 34/22 Q1004 decodes as: surface wind 300° at 12 kt, visibility 5,000 m in haze, no significant cloud, temperature 34 °C, dewpoint 22 °C, QNH 1004 hPa. The spread is 12 °C, so any convective cloud would base near 4,800 ft AGL; with NSC and haze present, expect no significant cloud but reduced visibility and a low-level inversion.
Traps
- Reading the dewpoint as the temperature, or quoting the cloud base in feet AMSL.
- Using QFE when the question asks for terrain clearance with QNH set.
- Treating TEMPO as a permanent change.