Terminal Aerodrome Forecast

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The Terminal Aerodrome Forecast ( TAF ) is an aviation weather forecast for larger airports. The form, content and meaning of the TAF are internationally standardized via ICAO guidelines.

A TAF consists of a header, information about wind and wind speed , visibility, current weather conditions, cloud height and degree of coverage for a maximum of 3 cloud levels , as well as forecast changes in these conditions within the validity period. The counterpart to the TAF is the METAR , which reflects the actual weather situation observed at the respective output time.

In Germany, TAFs are issued by the German Weather Service (DWD) four times a day at 6-hour intervals. The output times differ depending on the institution in the country that created it. As an example, these are 2300, 0500, 1100 and 1700 UTC. It is valid for 9, 24 or 30 hours in an area of ​​8 km (5 miles) around the airfield. Military airfields use different times. If the forecast changes significantly, the TAF is corrected with the new time (AMD).

General syntax

TAF
<Kennzeichen für Ergänzung (AMD) bzw. Korrektur (COR)>
<ICAO-Kennung des Flughafens/-platzes>
<Ausgabetag und -uhrzeit (UTC)>
<Gültigkeitszeitraum>
<Windrichtung und -stärke>
<Bodensicht>
<Bewölkung>
<voraussichtliche Änderungen mit Uhrzeitangabe>

units

The following units are used in Germany:

  • Horizontal distances: m . Example: bottom view.
  • Vertical distances: ft . Example: main cloud base, specified in 100 ft increments.
  • Speeds: kts . Example: wind speed.
  • Direction: degrees related to the geographic North Pole. Example: wind direction.
  • Time: All times are given absolutely with the help of two defined points in time. The reference system is always UTC .

International standard

ICAO member states can generally deviate from the specified standards, but usually only do so in details. In the USA z. B. an "unlimited" visibility is not specified with the group "9999" (10,000 m or more), but with "P6SM" ("plus 6 statute miles" - more than 6 country miles).

This article describes the German standard. Germany follows the ICAO standards.

example

A slightly longer TAF from September 4, 2011 from Frankfurt (EDDF) 

 TAF EDDF 041100Z 0412/0518
   22008KT 9999 SCT035
   TEMPO 0414/0420 SHRA BKN030CB
   PROB30 TEMPO 0414/0420 25015G25KT 2000 +TSRA BKN014
   TEMPO 0420/0502 4000 RA BKN014
   PROB30 TEMPO 0502/0508 4000 SHRA BR BKN012CB
   PROB30 TEMPO 0505/0515 26015G25KT

interpretation

The key for the interpretation of the weather phenomena is identical to that for METARs and is not explained again here.

interpretation
row content meaning
1 TAF head "TAF" for Airport EDDF ( EDDF ), created on the 4th of the month at 11: 00h UTC ( 041100Z ), valid from the 4th of the month 12: 00h UTC to the 5th of the month 18: 00h UTC ( 0412/0518 )
2 Coded weather: Forecast for weather from the start of validity Wind from 220 °, 8 knots ( 22008KT ). Clouds "scattered" at 3,500 feet ( SCT035 )
3 Temporary weather change within a period The following weather phenomena occur temporarily between ( TEMPO ) the 4th of the month, 14: 00h UTC to the 4th of the month, 20: 00h UTC ( 0414/0420 ).
4th Possible temporary weather change Temporarily to a "30% chance" ( PROB30 ) between ( TEMPO ) the fourth of the month, 14: 00h UTC and the fourth of the month, 20: 00h UTC ( 0414/0420 ) following weather phenomena occur.
5-7 Other temporary changes S. o.

Change groups

In contrast to the METAR, which only expresses the weather observed at the time of creation, the TAF can reproduce various weather conditions as a forecast over a longer period of time. The DWD explains:

"If a significant change is expected (reaching, exceeding or falling below defined threshold values, beginning and end of significant weather phenomena), the forecast period is divided. This is done with the help of change groups. All change groups are linked to a time group. "

Change groups are TAF-specific and are introduced with the help of the keywords TEMPO , BECMG and FM . If the occurrence of a condition described with TEMPO is uncertain, it can be assigned a percentage probability using the PROB keyword . This is basically either 30 or 40%.

FM
FMDDHHMM ...
The day of the month, the hour and the minute from which the new situation occurs is specified. After an FM keyword, the entire previously specified weather is obsolete and must be completely redefined.
BECMG
BECMG DDHH/DDHH ...
Between two points in time, given in day d. Month / hour d. Day , the weather changes from one permanent state to the next permanent state. Only the newly specified parameters change, what has not been redefined remains the same.
TEMPO
TEMPO DDHH/DDHH ...
Between two points in time, given in day d. Month / hour d. Day , the specified weather phenomena occur. The duration of the occurrence is generally less than an hour, and generally less than half of the specified period. The correct interpretation is "within this period the following weather phenomena occur at times : ..." .
PROB ..
PROB.. TEMPO DDHH/DDHH ...
Either PROB30 or PROB40 only . The described weather phenomena occur with the stated probability.

TAF corrections or amendments

Issued TAFs can be corrected or corrected retrospectively, should the need arise. The DWD explains:

"TAFs issued are corrected if serious deviations from the original forecast have occurred or are expected. A corrected TAF is marked with AMD (to amend: rectify). "

Examples

Here are some real-life examples of amended / corrected TAFs from September 4, 2011:

  • 'TAF AMD EDJA 041530Z 0416/0420 30010KT 4000 TSRA SCT012 BKN035CB BECMG 0416/0418 NSW SCT015 BKN040 TEMPO 0418/0420 RA=
  • 'TAF AMD EDTL 041655Z 0417/0424 CNL=
  • 'TAF AMD ETAD 0412/0511 19015KT 9999 SCT025 BKN030 QNH2983INS BECMG 0413/0414 21015G20KT 8000 -SHRA SCT025 BKN060 QNH2984INS BECMG 0418/0419 23007KT 9999 NSW SCT025 BKN100 QNH2983INS BECMG 0423/0424 20007KT 9999 BKN015 OVC040 QNH2983INS T23/0412Z T11/0503Z AMD 041225 LIMITED METWATCH 0412 TIL 0604=
  • 'TAF COR EDGS 041700Z 0418/0421 27006KT 9999 SCT015 TEMPO 0418/0421 20006KT 2500 RA BKN006=

Recent legal changes

With effect from November 5, 2008, the distinction between short (9 h) and long (24 h) TAF was abolished in Germany. The German Weather Service ( DWD ) is implementing the regulations of ICAO Annex 3, Amendment 74.

The validity period of a TAF is now extended to a maximum of 30 hours. In Germany, the 30-hour forecasts are only issued for the airports in Munich, Frankfurt, Cologne, Düsseldorf and Hamburg (ICAO ID: EDDM, EDDF, EDDK, EDDL and EDDH). The remaining airports / squares receive 24- or 9-hour forecasts.

The topicality in comparison to the earlier Short TAF is ensured by additions - marked by AMD - to the first edition.
Example: TAF AMD EDDM 061100Z ...

Corrections are indicated by COR .

In order to ensure clarity, the time groups now also contain the validity date.

Example: TAF EDDM 061100Z 06 12/ 07 18 - the forecast period is valid from the 6th of the month, 12:00 UTC to 7th, 18:00 UTC.

If the sky is below 1524 m, NSC ("no significant clouds") is indicated if the conditions for " CAVOK " are not sufficient. However, both specifications only describe a state up to 1524 m (5000  ft ).

Individual evidence

  1. ↑ a b c d TAF - explanations of the DWD on TAF

Web links