How to read a terminal aerodrome forecast with confidence
A Terminal Aerodrome Forecast, or TAF, is a time-based prediction of the weather expected at or near an airport. It gives pilots a planning picture for wind, visibility, significant weather and cloud during a defined validity period. Unlike a METAR, which describes conditions observed now, a TAF looks ahead and explains how those conditions may change.
For Australian pilots, understanding the forecast means doing more than decoding groups of letters and numbers. A departure from Bankstown, a training circuit at Moorabbin, or a cross-country flight through Queensland can involve rapidly changing coastal winds, inland heat, thunderstorms and terrain effects. Learning to read each part of the forecast helps connect the coded message with a practical go/no-go decision.
Start with the forecast header
A TAF normally begins with the report type, the aerodrome identifier and the period for which the forecast applies. A typical opening might look like this:
TAF YSCB 101100Z 1012/1118
“TAF” identifies the product. “YSCB” is Canberra Airport, using the four-letter ICAO location indicator. The next group, “101100Z”, shows the issue time: the 10th day of the month at 1100 UTC. The final group, “1012/1118”, shows that the forecast is valid from 1200 UTC on the 10th until 1800 UTC on the 11th.
Australian aviation weather is issued in UTC, also known as Zulu time. Local conversion is essential because Australian states use different standard and daylight-saving arrangements. A forecast issued at 1100Z may be late evening in eastern Australia during daylight-saving time, while Western Australia uses a different local offset. A pilot should convert both the issue time and validity period before assessing a morning or afternoon flight.
Some forecasts are marked “AMD”, meaning amended. An amended TAF replaces the earlier forecast because the expected conditions have changed significantly or the original forecast no longer meets operational requirements. A “COR” marking indicates a correction to an error. Always check the issue time and status before relying on a forecast copied from an earlier briefing.
Decode time, wind and visibility groups
Wind is usually shown as direction in degrees true followed by speed in knots. For example, “18012KT” means wind from 180 degrees true at 12 knots. “VRB05KT” indicates variable direction at 5 knots. A group such as “18012G22KT” means a mean wind of 12 knots from 180 degrees with gusts up to 22 knots.
The wind direction is where the wind is coming from, not where it is travelling. A southerly wind therefore comes from the south. This matters when comparing the forecast with runway orientation. At an airport such as Melbourne’s Moorabbin, a forecast southerly may produce a useful runway component, while a crosswind or tailwind can become significant as the wind changes through the day. Check the forecast against the runway limits for the aircraft and the pilot’s current experience.
A wind group of “00000KT” means calm conditions. A direction followed by “V” and another direction, such as “18012KT 150V220”, means the wind is expected to vary between 150 and 220 degrees. This can be particularly relevant around coastal aerodromes, where a sea-breeze front may alter the wind direction quite quickly during the arvo.
Visibility is expressed in metres in Australian TAFs. “9999” means visibility of 10 kilometres or more. “4000” means 4,000 metres, while “0800” means 800 metres. Visibility may be reduced by mist, fog, smoke, dust, rain or showers, and the cause is usually shown in the weather group that follows.
Read weather and cloud groups together
Weather phenomena use standard abbreviations. “RA” means rain, “SHRA” means rain showers, “TS” means thunderstorm, “DZ” means drizzle, “BR” means mist and “FG” means fog. “-RA” indicates light rain and “+RA” heavy rain. “TSRA” describes thunderstorms with rain, while “VCTS” means thunderstorms are expected in the vicinity of the aerodrome rather than directly overhead.
Cloud groups show the amount, base and type. “SCT020” means scattered cloud with a base at 2,000 feet above aerodrome level. “BKN015” means broken cloud at 1,500 feet, and “OVC008” means overcast cloud at 800 feet. Cloud heights in a TAF are given in hundreds of feet, so “BKN045” represents a broken layer based at 4,500 feet.
The cloud amount is operationally important. Few and scattered layers may leave broad areas of sky clear, while broken and overcast layers can determine whether visual operations remain practical. “CB” identifies cumulonimbus, the cloud associated with thunderstorms, and “TCU” identifies towering cumulus. These groups deserve special attention because turbulence, lightning, hail, heavy rain and severe wind shifts may exist well beyond the visible rain shaft.
| TAF group | Meaning | Operational significance |
|---|---|---|
9999 |
Visibility of 10 km or more | Generally unrestricted visibility, subject to cloud and weather |
-RA |
Light rain | May reduce visibility and affect runway surface conditions |
SHRA |
Rain showers | Conditions can change rapidly across the aerodrome |
BKN020 |
Broken cloud at 2,000 ft | Important for circuit, VFR and approach planning |
OVC008 |
Overcast cloud at 800 ft | May create low-ceiling or instrument conditions |
VCTS |
Thunderstorms in the vicinity | Expect possible gusts, lightning, rain and route disruption |
WS020/18040KT |
Low-level wind shear below 2,000 ft | Significant take-off and landing hazard |
A TAF can contain several weather and cloud groups at once. Read them as a combined scenario rather than treating each item separately. For example, 4,000 metres visibility in moderate rain with a broken ceiling at 1,500 feet creates a different operational picture from 4,000 metres in haze with a scattered layer at 1,500 feet.
Understand change groups and probabilities
The initial weather groups apply from the beginning of the validity period until another change group takes effect. “FM” means “from” and introduces a relatively rapid, permanent change. For example, “FM101800 22018G30KT 5000 SHRA BKN020” means that from 1800 UTC on the 10th, the forecast changes to a south-westerly wind at 18 knots with gusts to 30, visibility of 5,000 metres in showers and broken cloud at 2,000 feet.
“BECMG” means “becoming”. It describes a gradual change expected during a stated time window. A group such as “BECMG 1014/1016 18012KT” means the wind is expected to become 180 degrees at 12 knots between 1400 and 1600 UTC. During that window, either the earlier or later conditions may be present.
“TEMPO” describes temporary fluctuations expected to last for a limited period, generally less than an hour at a time and not continuously across the whole window. A forecast such as “TEMPO 1016/1020 3000 TSRA BKN012CB” warns that, between 1600 and 2000 UTC, temporary periods of 3,000-metre visibility, thunderstorms with rain and broken cumulonimbus cloud at 1,200 feet may occur.
Probability groups show uncertainty. “PROB30” means a 30 per cent probability of the conditions occurring during the specified period; “PROB40” means 40 per cent where that format is used. A probability group is not a promise that the weather will stay acceptable the other 60 or 70 per cent of the time. For a solo student, night flight or long trip to a remote aerodrome, a low-probability storm may still be a decisive planning concern.
Apply the forecast to an Australian flight
A TAF covers the aerodrome area, not every kilometre of the route. A forecast for Alice Springs does not describe conditions over the MacDonnell Ranges, and a forecast for Cairns does not fully capture weather developing over the Atherton Tablelands. Mountain flying requires a separate assessment of cloud movement, ridge clearance, turbulence, winds aloft and escape options.
Terrain and heat also influence how a forecast should be interpreted. In summer, a TAF for a Brisbane-area airport may show manageable conditions while thunderstorms build inland or along the ranges. Around Perth, a morning easterly can give way to a stronger afternoon sea breeze. In Tasmania and Victoria, a forecast involving low cloud, frontal rain or strong winds may be more consequential near exposed terrain than the airport code alone suggests.
Compare the TAF with the METAR, trend information, area forecasts, weather radar, satellite imagery, NOTAMs and the aircraft’s performance limitations. If the current observation is already worse than the forecast, treat that discrepancy as useful evidence rather than waiting for the forecast to become accurate. The forecast is one part of a weather picture, not a substitute for monitoring conditions before departure and during the flight.
Australian pilots should also account for the practical shape of the trip. A local flight near Sydney may have several suitable diversion aerodromes, while a long leg across sparsely populated parts of Western Australia may offer few alternatives. At a busy training airport, circuit delays can consume the margin built into a weather plan. At a regional strip, fuel, lighting, runway surface and opening hours may matter as much as the TAF itself.
Turn coded information into a decision
Begin by identifying the most restrictive likely condition during the flight: the strongest wind and gust, lowest visibility, lowest ceiling, significant precipitation, thunderstorm risk or wind shear. Then compare that condition with the aircraft, pilot qualifications, route, runway, alternates and personal limits. A forecast that is legally suitable may still be unsuitable for a newly qualified pilot or a pilot returning after a break.
Keep medical and operational currency in the same planning process. A pilot organising a flight should ensure that the relevant medical certificate, licence privileges and recency requirements are current; guidance on medical certificate currency can help keep that part of the preparation visible rather than treating weather as the only limitation.
A useful briefing habit is to translate the coded forecast into plain language. For example: “The first part of the flight should have light south-easterly winds and good visibility, but showers may develop after 0600Z, with a lower broken ceiling and gusty winds after 0800Z.” If the forecast cannot be explained in ordinary words, it has probably not yet been interpreted fully.
Finally, revisit the TAF as departure approaches. Look for amendments, compare the latest METAR with the predicted conditions and check whether the expected trend is actually occurring. Regular practice with structured weather training can reinforce the difference between decoding a forecast and using it in a sound aeronautical decision. The aim is a clear understanding of what weather is expected, when it may change, how certain that change is and what action follows if the forecast proves wrong.