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IDAC Air Traffic Controller (CTA) study materials
IDAC Air Traffic Controller (CTA) study resources

IDAC Air Traffic Controller (CTA): Meteorology

IDAC Air Traffic Controller (CTA) · Work through your exam, one topic at a time.

All guide sections

Meteorology

This domain tests decoding of METAR, TAF and trend information, correct altimetry, and recognition of hazardous weather with the ATS response it triggers. Questions are usually applied: a coded report, an altimeter question, or a weather situation requiring a SIGMET, an alert or a change of runway.

METAR and TAF

  • METAR structure: type and time (day/hour/minute Z), surface wind (dddffKT or VRB, gusts G), visibility (metres, or CAVOK), RVR, present weather, cloud (FEW/SCT/BKN/OVC with base in hundreds of feet, CB/TCU), temperature and dewpoint, QNH (Q = hPa, A = inHg), then trend.
  • SPECI reports significant changes; TAF gives a validity period with change groups FM, TEMPO, BECMG, PROB30/40.
  • Weather groups: intensity +/−, descriptor (TS, SH, FZ, BL), precipitation (RA, SN, DZ, GR), obscuration (BR, FG, HZ), other (SQ, FC, PO).

Altimetry

  • QNH gives elevation when on the ground; QFE gives height above a datum; QNE is standard pressure 1013.25 hPa at the transition level.
  • Transition altitude is where climb changes from QNH to standard; transition level where descent changes back. The transition layer is never used for level flight.
  • Rule of thumb: about 27 ft per hPa (34 ft per inHg). "From high to low, look out below." Cold air makes the altimeter over-read, so published low-temperature corrections are needed on approach.

Hazardous weather

Thunderstorms (downbursts, microbursts, hail, lightning, severe turbulence), wind shear and low-level wind shear alerts, airframe icing, mountain waves, volcanic ash, fog and low visibility, and the SIGMET/AIRMET system that warns of them.

Worked example

MDSD 121800Z 09012G22KT 8000 -TSRA SCT016CB BKN070 26/24 Q1012. Reasoning: wind 090° at 12 kt gusting 22; visibility 8 km; light thunderstorm with rain; scattered cumulonimbus base 1600 ft, broken 7000 ft; temperature 26 °C, dewpoint 24 °C (high humidity, low spread); QNH 1012 hPa. Operational significance: CB with a small temperature/dewpoint spread - expect wind shear and possible microburst on approach.

Traps

Reading gusts as mean wind; confusing CB with TCU; mixing Q (hPa) and A (inHg); mistaking a TEMPO group for a permanent change; assuming a TAF is a forecast for the aerodrome only and not its vicinity.