How to decode a METAR and TAF, with Indian examples

A METAR tells you the weather at an aerodrome right now. A TAF tells you what it is expected to do over the next 6 to 30 hours. Both use the same fixed code, in the same order, every time. Learn the order once and you can read any report in India or abroad.

METAR, SPECI and TAF: what each one is

The order never changes

Here is a typical (illustrative) Delhi METAR:

METAR VIDP 050530Z 27008KT 240V300 3000 HZ FEW020 SCT100 31/18 Q1008 NOSIG

Memory aid: "Who Visits When Clouds Tell Pilots Tomorrow?" Wind, Visibility, Weather, Cloud, Temperature, Pressure, Trend.

Station codes and time

Indian aerodromes start with V. The second letter shows the flight information region: VI for Delhi (VIDP, VILK Lucknow), VA for Mumbai (VABB, VAAH Ahmedabad), VO for Chennai (VOMM, VOBL Bengaluru) and VE for Kolkata (VECC, VEGT Guwahati). These four-letter ICAO codes are not the three-letter IATA codes on your ticket (DEL, BOM).

All times are UTC, marked Z. India Standard Time is UTC + 5:30, so 0530Z is 1100 IST. In the exam, convert to local time only when the question asks.

Wind

Three digits give the direction in degrees true, rounded to 10°, the wind is blowing from. The next two (or three) digits give the 10-minute mean speed.

• 00000KT: calm.
• 25015G28KT: 15 kt gusting 28 kt. A gust is reported when the peak is at least 10 kt above the mean.
• 31012KT 280V350: the direction varies by 60° or more (but less than 180°) with a mean speed of 3 kt or more.
• VRB02KT: variable, used for light winds below 3 kt, or when the direction varies by 180° or more.

Visibility, RVR and CAVOK

Visibility is in metres: 0800 is 800 m and 9999 means 10 km or more. A minimum with a direction is added when it is below 1,500 m, or below half the prevailing visibility and below 5,000 m, as in 3000 1200SW.

Runway visual range is reported when the visibility or RVR is below 1,500 m: R28/0550U is runway 28, 550 m, improving. P means more than the system can measure, M means less, and U, D or N show the tendency (up, down, no change).

CAVOK replaces visibility, weather and cloud when visibility is 10 km or more, there is no cloud below 5,000 ft (or the highest minimum sector altitude, whichever is higher), no CB or TCU, and no significant weather.

Present weather

Weather is built from an intensity (- light, nothing for moderate, + heavy, VC in the vicinity), a descriptor (SH showers, TS thunderstorm, FZ freezing, BC patches, MI shallow) and the phenomenon (RA rain, DZ drizzle, FG fog, BR mist, HZ haze, DU dust).

Exam point: mist (BR) is reported when visibility is 1,000 to 5,000 m, fog (FG) when it is below 1,000 m. Haze is dry particles; mist is water droplets, so a small temperature and dew point spread points to BR.

Cloud

Height follows in hundreds of feet above the aerodrome: BKN015 is broken at 1,500 ft. CB or TCU is added for cumulonimbus or towering cumulus. VV002 means the sky is obscured with a vertical visibility of 200 ft. The ceiling is the lowest BKN or OVC layer below 20,000 ft.

Temperature and pressure

31/18 is temperature and dew point in whole degrees Celsius; M02 is minus 2. A spread of 2–3 °C or less at night with light wind warns of fog or low cloud. Q1008 is QNH 1008 hPa. Watch the double meaning of M: minus in a temperature, "less than" in an RVR.

Reading a TAF

TAF VOMM 050500Z 0506/0612 08010KT 9999 SCT020 BECMG 0508/0510 12015KT TEMPO 0512/0518 4000 SHRA BKN014

This illustrative Chennai TAF was issued on the 5th at 0500 UTC and is valid from 0600 UTC on the 5th to 1200 UTC on the 6th. It starts with wind 080° at 10 kt, 10 km or more and scattered cloud at 2,000 ft. Between 0800 and 1000 the wind becomes 120° at 15 kt and stays. Between 1200 and 1800 there are temporary spells of 4,000 m in rain showers with broken cloud at 1,400 ft.

Exam trap: 0524 in a validity group means 2400 UTC on the 5th, which is midnight at the end of the 5th.

Two worked examples

Both reports are illustrative, written for practice.

METAR VIDP 120130Z 00000KT 0800 R28/0650N R29/0700D FG NSC 09/08 Q1020 BECMG FM0300 2000 BR

Delhi, 12th at 0130 UTC (0700 IST). Calm. Visibility 800 m. RVR runway 28 is 650 m with no change; runway 29 is 700 m and falling. Fog, no significant cloud, 9 °C with a dew point of 8 °C, QNH 1020. Becoming 2,000 m in mist from 0300 UTC.

METAR VABB 180930Z 25018G30KT 220V290 3000 +TSRA SCT012 FEW025CB BKN080 27/25 Q1002 RETS TEMPO 1500 TSRA

Mumbai, 18th at 0930 UTC. Wind 250° at 18 gusting 30 kt, varying 220°–290°. 3,000 m in a thunderstorm with heavy rain. Scattered at 1,200 ft, a few CB at 2,500 ft, broken at 8,000 ft. 27/25 °C, QNH 1002. Recent thunderstorm. Temporarily 1,500 m in thunderstorm and rain.