Decoding a TAF
A Terminal Area Forecast (TAF) is a weather forecast that applies to an area within 5 nm of an aerodrome.
The TAF consists of the following information:
- Message identification (ie TAF)
- Location identifier
- Time of origin (UTC)
- Validity period
- Forecast surface wind
- Forecast visibility
- Forecast significant weather
- Forecast cloud amount and height
- Forecast significant changes and variations
- Possibility of poor visibility
- Statement of turbulence
- Forecast temperatures and QNH
Example:
TAF AMD YSBK 241854Z 2420/2508 VRB03KT CAVOK FM242300 02010KT 9999 SCT040 BKN100 PROB30 2420/2423 2000 MIST INTER 2506/2508 7000 LIGHT SHOWERS OF RAIN BKN020 T 17 21 19 15 Q 1016 1014 1013 1013
TAF means that this is a Terminal Area Forecast.
AMD means that the TAF has been amended since it's original issue time.
YSBK is the location (Bankstown in this case)
241854Z is the issue date and time - 24th day of the month, 1854Z (for Bankstown - add 10 h to this to get local time, or add 11 h during Daylight Savings)
2420/2508 is the validity period 24th day 2000Z to 25th day 0800Z.
VRB03KT is the wind from variable direction at 3 knots
CAVOK means Ceiling and Visibility OK (Visibility greater than 10 km, no cloud below 5000 ft, no cumulonimbus, no precipitation, thunderstorms, shallow fog, low drifting snow, or dust devils).
FM242300 means that from 2300Z on the 24th the wind will be 02010KT .Wind direction in degrees from True North (020 deg True) and speed (10 kts) and 9999 will be the visibility in metres (9999 means greater than 10 km) and
SCT040 BKN100 are the cloud amounts and heights above the aerodrome (in 100's of feet)
Cloud amount is expressed as SKC, FEW, SCT, BKN or OVC
SKC (sky clear) is nil cloud
FEW (few) is 1-2 OKTAS (eights),
SCT (scattered) is 3-4 OKTAS
BKN (broken) is 5-7 OKTAS
OVC (overcast) is 8 OKTAS
The cloud types of Cumulonimbus and Towering Cumulus will be indicated with abbreviations CB and TCU respectively (eg SCT040CB is scattered Cumulonimbus cloud base 4000 ft).
In this case 3-4 OKTAS with a base of 4000 ft, 5-7 OKTAS with a base of 10 000 ft.
PROB30 2420/2423 2000 MIST means that between 2000Z on the 24th and 2300Z on the 24th there is a 30% probability of the visibility dropping to 2000 m in mist.
INTER 2506/2508 7000 LIGHT SHOWERS OF RAIN BKN020 the forecast indicates that rain showers are due from 0600Z on the 25th to the end of the forecast. For periods up to 30 minutes (INTER or intermittent) the visibility is expected to reduce to 7000 m and the cloud lowering to 5-7 OKTAS at 2000 ft. A temporary deterioration (TEMPO) would be for up to 60 min.
T 17 21 19 15 Q 1016 1014 1013 1013 represent the Temperature and QNH in 3 hourly intervals from the start of the forecast period. In this case at 2000Z the temperature is forecast to be 17 deg C and QNH 1016 hPa, at 0500Z the forecast temperature is 15deg C and QHN 1013 hPa.
Decoding A METAR
A METAR is a statement of actual weather conditions at an airport. METAR information if normally supplied from an automated weather station, and may have some information appended to it from an ATC control tower.
A METAR contains
- Message identification (ie METAR or SPECI)
- Location identifier
- Time of origin
- Surface wind with gusts if appropriate
- Visibility including sector variations
- Present weather
- Cloud amount and height above aerodrome
- Temperature and Dew Point temperature
- QNH
Supplementary information
A SPECI is a METAR that is issued at other than the scheduled routine times.
Example
METAR YSBK 250230Z 31008KT 9999 / / SCT025 19/04 Q1015 RMK RF00.1/012.0
METAR says this is a METAR
YSBK is the location
250230Z is the time the observation was taken. 0230Z on the 25th
31008KT is the wind with reference to degrees from True north (310 deg T at 8 kts)
Visibility 9999 means the visibility is greater than 10 km
/ / means this part of the METAR is not available (ie cloud and visibility not available from an automated weather station)
SCT025 is scattered cloud base 2500 ft
19/04 is the temperature (19 deg C) and dewpoint (4 deg C). Temperature and dew point can be used to calculate relative humidity.
Q1015 is the QNH.
RMK precedes any remarks appended to the METAR.
RF00.1/012.0 is the rainfall in mm. The first number is rainfall in the last 10 minutes (0.1 mm), and the second the rainfall since 9 am local time (12.0 mm).