TAF decoder

What the TAF decoder displays

A TAF is a forecast for weather conditions at an airport over a stated period. It is different from a METAR, which reports observed conditions. This decoder separates a pasted TAF into its station, issue time, validity period, initial forecast groups, and later changes such as FM, BECMG, TEMPO, and PROB.

The decoded forecast shows wind, visibility, significant weather, cloud layers, and a ceiling when the corresponding groups are present. It also keeps the encoded text for each group visible, so you can compare the plain-language description with the original. The decoder processes only the report entered here. It does not retrieve a current forecast.

How to use the decoder

Paste a complete TAF into the input. The report and decoded groups update as you type, and the entered text is mirrored in the URL so a specific example can be shared. Select Use example to restore the sample report or Clear to remove the input.

The issue and forecast times in a TAF use UTC. The report gives day numbers and times, not a complete calendar date. This decoder labels them as days and UTC times rather than guessing a month or year. Use the source that supplied the forecast to establish its full date and age.

Read the header and initial forecast

Consider this shortened example:

TAF KJFK 121130Z 1212/1318 18012G20KT P6SM FEW025 SCT050

The cloud amounts describe sky coverage, and the coded heights are reported in hundreds of feet above the aerodrome. A broken or overcast layer, or vertical visibility, can define the reported ceiling. The decoder displays the lowest such layer when one is included.

An amended or corrected forecast is marked in the result. CNL identifies a canceled TAF, while NIL indicates that no report data is supplied. These status groups do not provide forecast conditions.

Understand forecast changes

Change groups describe weather expected during portions of the TAF validity period. Their timing and meaning are different, so read the group label and interval along with the wind, visibility, weather, and cloud groups it contains.

The exact forms and combinations vary by report. For example, probability and temporary groups can appear together. This tool preserves each parsed group and its original encoded text rather than flattening the entire forecast into one condition. If a change group omits wind, visibility, or clouds, that does not necessarily mean the prevailing forecast has ended; read it in the context of the preceding groups.

Worked example

In the sample above, the initial forecast gives wind from 180 degrees at 12 knots with gusts to 20 knots. Visibility is more than 6 statute miles. The first two cloud layers are few at 2,500 feet and scattered at 5,000 feet.

If the report then includes TEMPO 1214/1218 3SM -SHRA BKN020, the decoder identifies a temporary period from day 12 at 14:00 UTC to day 12 at 18:00 UTC. The groups describe 3 statute miles visibility, light rain showers, and a broken layer with a base at 2,000 feet. A later FM122000 starts a new prevailing forecast at 20:00 UTC on day 12. These are forecast groups, not observations of what has already occurred.

Common interpretation mistakes

Do not treat a TAF as a METAR or assume it describes conditions along an entire route. Its forecast is for the named aerodrome and the report's stated validity period. A separate weather review is needed for other locations and the space between them.

Do not read a temporary or probability group as if it replaces every condition in the initial forecast. Those groups describe additional changes over their own intervals. In particular, an omitted group in a partial change should not be translated as a guaranteed absence of that weather element.

Do not infer the month or year from the day numbers alone. TAF validity periods can cross a month boundary, and the same day number occurs in every month. Confirm the full issue time and date with the official source.

Limitations and verification

Automated parsing makes common report groups easier to review, but it cannot explain every national format, uncommon code, or forecast nuance. A parser can also reject malformed or unsupported input. Compare unfamiliar groups with official references and the source forecast.

This tool decodes text supplied by the user. It does not establish whether a forecast is current, retrieve amendments, or determine the weather along a route. A decoded TAF is for training and reference only, not an operational flight decision. Consult current official weather products, advisories, applicable publications, and the aircraft POH or AFM as appropriate.

Sources and methodology

The FAA Aeronautical Information Manual, chapter 7 describes aviation weather reports and forecast products. The NOAA Aviation Weather Center Data API distributes weather data, including TAFs. This page parses the entered report locally with metar-taf-parser; it does not request forecast data from the NOAA API.

Related tools and resources

• METAR decoder
• Airport weather and flight planning