Terminal Aerodrome Forecast
Encyclopedia
In meteorology
and aviation
, TAF is a format for reporting weather forecast information, particularly as it relates to aviation. "TAF" is an acronym of Terminal Aerodrome
Forecast or, in some countries, Terminal Area Forecast.
TAFs apply to a five statute mile radius from the center of the airport runway complex. Generally, TAFs can apply to a 9- or 12-hour forecast; some TAFs cover an 18- or 24-hour period; and as of November 5, 2008, TAFs for some major airports cover 30 hours periods. The date/time group reflects the new 30 hour period in Coordinated Universal Time (UTC), as always.
TAFs complement and use similar encoding to METAR
reports.
They are produced by a human forecaster based on the ground. For this reason there are fewer TAF locations than there are METARs. TAFs can be more accurate than Numerical Weather Forecasts
, since they take into account local, small-scale, geographic effects.
In the United States the weather forecaster responsible for a TAF is not usually stationed at the location to which the TAF applies. The forecasters usually work from a centralised location responsible for many TAFs in a state or region, many of which are over one hundred miles from the forecaster's location. In contrast, a TTF
(Trend Type Forecast), which is similar to a TAF, is always produced by a person on-site where the TTF applies. In the United Kingdom
most TAFs at military airfields are produced locally, however TAFs for civil airfields are produced at the Met Office
headquarters in Exeter
.
The United States Air Force
employs active duty enlisted personnel as TAF writers. Air Force weather personnel are responsible for providing weather support for all Air Force and Army
operations.
Different countries use different change criteria for their weather groups. In the United Kingdom, TAFs for Military airfields use Colour States as one of the change criteria. Civil airfields in the UK use slightly different criteria.
The first line contains identification and validity times.
The remainder of the first line and the second line contain the initial forecast conditions. Variations of the codes used for various weather conditions are many - see http://aviationweather.gov/static/help/taf-decode.php.
Each line beginning with FM starts a new forecast period.
The remainder of the line has similar formatting to the other forecast lines.
The final line is for errata, comments, and remarks.
.
In this example the METAR indicates it is from EGYM (RAF Marham
) at 1350 UTC on Day 29. The observation follows (see METAR
for explanation), with the Trend added to the end of the observation.
The Trend reads TEMPO 7000 -RADZ SCT020 WHT i.e. Temporary deterioration to 7 km visibility in slight rain or drizzle with scattered at 2000 ft, colour state
White.
Meteorology
Meteorology is the interdisciplinary scientific study of the atmosphere. Studies in the field stretch back millennia, though significant progress in meteorology did not occur until the 18th century. The 19th century saw breakthroughs occur after observing networks developed across several countries...
and aviation
Aviation
Aviation is the design, development, production, operation, and use of aircraft, especially heavier-than-air aircraft. Aviation is derived from avis, the Latin word for bird.-History:...
, TAF is a format for reporting weather forecast information, particularly as it relates to aviation. "TAF" is an acronym of Terminal Aerodrome
Aerodrome
An aerodrome, airdrome or airfield is a term for any location from which aircraft flight operations take place, regardless of whether they involve cargo, passengers or neither...
Forecast or, in some countries, Terminal Area Forecast.
TAFs apply to a five statute mile radius from the center of the airport runway complex. Generally, TAFs can apply to a 9- or 12-hour forecast; some TAFs cover an 18- or 24-hour period; and as of November 5, 2008, TAFs for some major airports cover 30 hours periods. The date/time group reflects the new 30 hour period in Coordinated Universal Time (UTC), as always.
TAFs complement and use similar encoding to METAR
METAR
METAR is a format for reporting weather information. A METAR weather report is predominantly used by pilots in fulfillment of a part of a pre-flight weather briefing, and by meteorologists, who use aggregated METAR information to assist in weather forecasting....
reports.
They are produced by a human forecaster based on the ground. For this reason there are fewer TAF locations than there are METARs. TAFs can be more accurate than Numerical Weather Forecasts
Numerical weather prediction
Numerical weather prediction uses mathematical models of the atmosphere and oceans to predict the weather based on current weather conditions. Though first attempted in the 1920s, it was not until the advent of computer simulation in the 1950s that numerical weather predictions produced realistic...
, since they take into account local, small-scale, geographic effects.
In the United States the weather forecaster responsible for a TAF is not usually stationed at the location to which the TAF applies. The forecasters usually work from a centralised location responsible for many TAFs in a state or region, many of which are over one hundred miles from the forecaster's location. In contrast, a TTF
Trend Type Forecast
A TTF or Trend Type Forecast also known simply as a Trend, is an aviation weather forecast written by a real person on location at a major airport or military base...
(Trend Type Forecast), which is similar to a TAF, is always produced by a person on-site where the TTF applies. In the United Kingdom
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
most TAFs at military airfields are produced locally, however TAFs for civil airfields are produced at the Met Office
Met Office
The Met Office , is the United Kingdom's national weather service, and a trading fund of the Department for Business, Innovation and Skills...
headquarters in Exeter
Exeter
Exeter is a historic city in Devon, England. It lies within the ceremonial county of Devon, of which it is the county town as well as the home of Devon County Council. Currently the administrative area has the status of a non-metropolitan district, and is therefore under the administration of the...
.
The United States Air Force
United States Air Force
The United States Air Force is the aerial warfare service branch of the United States Armed Forces and one of the American uniformed services. Initially part of the United States Army, the USAF was formed as a separate branch of the military on September 18, 1947 under the National Security Act of...
employs active duty enlisted personnel as TAF writers. Air Force weather personnel are responsible for providing weather support for all Air Force and Army
Army
An army An army An army (from Latin arma "arms, weapons" via Old French armée, "armed" (feminine), in the broadest sense, is the land-based military of a nation or state. It may also include other branches of the military such as the air force via means of aviation corps...
operations.
Different countries use different change criteria for their weather groups. In the United Kingdom, TAFs for Military airfields use Colour States as one of the change criteria. Civil airfields in the UK use slightly different criteria.
TAF Code
This TAF example of a 30-hour TAF, released on November 5, 2008 at 1730 UTC:TAF KXYZ 051730Z 0518/0624 31008KT
3SM -SHRA BKN020
FM052300 30006KT 5SM -SHRA OVC030
PROB30 0604/0606 VRB20G35KT 1SM
TSRA BKN015CB
FM 060600 250010KT 4SM -SHRA OVC050
TEMPO 0608/0611 2SM -SHRA OVC030=
RMK NXT FCST BY 00Z=
The first line contains identification and validity times.
- TAF indicates that the following is a terminal area forecast.
- KXYZ indicates the airport to which the forecast applies (ICAO airport codeICAO airport codeThe ICAO airport code or location indicator is a four-character alphanumeric code designating each airport around the world. These codes are defined by the International Civil Aviation Organization, and published in ICAO Document 7910: Location Indicators.The ICAO codes are used by air traffic...
). - 051730Z indicates that the report was issued on the 5th of the month at 1730 UTC (also known as zulu).
- 0518/0624 indicates that the report is valid from the 5th at 1800 UTC until the 6th at 2400 UTC.
The remainder of the first line and the second line contain the initial forecast conditions. Variations of the codes used for various weather conditions are many - see http://aviationweather.gov/static/help/taf-decode.php.
- 31008KT indicates that the wind will be from 310 degrees true at 8 knots.
- 3SM -SHRA BKN020 indicates that visibility will be 3 statute miles in light (-) showers (SH) of rain (RA), with a broken ceiling (between 5/8 and 7/8 of the sky covered) at 2,000 feet AGL.
Each line beginning with FM starts a new forecast period.
- FM052300 indicates the next period lasts from (FM) the 5th at 2300 UTC to the 6th at 0000 UTC.
The remainder of the line has similar formatting to the other forecast lines.
The final line is for errata, comments, and remarks.
- RMK NXT FCST BY 00Z indicates a remark that the next forecast will be issued by 0000 UTC.
TAF Rules
TAFs must follow a set of rules that define what must be placed in each line and what criteria require a new line. There are four different lines in a TAF. The first one gives location, valid time and given weather for that time until the next line of the forecast. A BECMG (becoming) line indicates that in the period given, the weather will start to change from the previous line to the next line; an FM (from) line indicates that after the given time, the weather will be what the line states; and a TEMPO lasts for no more than one hour on any one occasion and the total time spent in those conditions will not add up to more than half the period.Trend
A Trend is a truncated version of a TAF giving the expected conditions in a two hour period following the issue of an observation. This short period forecast is appended to the end of a METARMETAR
METAR is a format for reporting weather information. A METAR weather report is predominantly used by pilots in fulfillment of a part of a pre-flight weather briefing, and by meteorologists, who use aggregated METAR information to assist in weather forecasting....
.
METAR EGYM 291350Z 29010KT 8000 -RADZ FEW010 SCT037 OVC043
10/07 Q1008 BLU TEMPO 7000 -RADZ SCT020 WHT=
In this example the METAR indicates it is from EGYM (RAF Marham
RAF Marham
Royal Air Force Station Marham, more commonly known as RAF Marham, is a Royal Air Force station; a military airbase, near the village of Marham in the English county of Norfolk, East Anglia....
) at 1350 UTC on Day 29. The observation follows (see METAR
METAR
METAR is a format for reporting weather information. A METAR weather report is predominantly used by pilots in fulfillment of a part of a pre-flight weather briefing, and by meteorologists, who use aggregated METAR information to assist in weather forecasting....
for explanation), with the Trend added to the end of the observation.
The Trend reads TEMPO 7000 -RADZ SCT020 WHT i.e. Temporary deterioration to 7 km visibility in slight rain or drizzle with scattered at 2000 ft, colour state
Colour state
Colour States are a system used for quickly showing meteorological conditions.Meteorological colour states are determined by the relevant worst condition from the visibility and significant cloud height. In the USA and parts of Europe the lowest significant cloud layer is 5 oktas or more; in the...
White.