Meteorology
This domain tests the atmosphere, altimetry, weather systems affecting Oman and the decoding of reports and forecasts.
Atmosphere and altimetry
- ISA: sea level 15 C, 1013.25 hPa, lapse rate 1.98 C per 1,000 ft up to the tropopause near 36,090 ft.
- QNH set on the sub-scale gives altitude above mean sea level; QFE gives height above the aerodrome; QNE (1013.25) is used above the transition level to give flight levels.
- Flying from high to low pressure without resetting the altimeter leaves the aircraft lower than indicated - a classic controlled-flight-into-terrain scenario. The same applies flying from cold to warm air.
- Below 10,000 ft the altimeter error is about 30 ft per hPa.
Oman climate
- Summer temperatures above 45 C produce extreme density altitude and degraded performance; early departures are not merely a comfort choice.
- The shamal is a north-westerly wind that raises dust and sand, reducing visibility to a few kilometres and creating severe low-level turbulence.
- The khareef monsoon affects Dhofar from June to September with low cloud, drizzle and poor visibility around Salalah.
- Sea breezes are strong along the coast; inland convection builds through the afternoon.
Clouds, icing and thunderstorms
- Cumulonimbus brings hail, severe turbulence, icing, microbursts and lightning; avoid by at least 20 nm visually and never beneath the anvil.
- Airframe icing requires visible moisture and temperatures near or below freezing; carburettor icing can occur in much warmer air.
Worked example
Decode: OOMS 120950Z 32012KT 5000 HZ SCT030 38/24 Q1002. Muscat, 12th, 0950 UTC, wind 320 at 12 kt, visibility 5,000 m in haze, scattered cloud at 3,000 ft, temperature 38 C, dewpoint 24 C, QNH 1002 hPa. Density altitude will be well above field elevation - plan accordingly.
Traps
Confusing QNE with QNH; forgetting the 30 ft per hPa rule; assuming haze is harmless when it is Oman's most common visibility restriction.