Format for reporting aviation weather forecast information
In
meteorology
and
aviation
,
terminal aerodrome forecast
(
TAF
) is a format for reporting
weather forecast
information,
[1]
particularly as it relates to aviation. TAFs are issued at least four times a day, every six hours, for major civil airfields: 0000, 0600, 1200 and 1800 UTC,
[2]
and generally apply to a 24- or 30-hour period, and an area within approximately five
statute miles
(8.0 km) (or 5 nautical miles (9.3 km) in Canada) from the center of an airport runway complex. TAFs are issued every three hours for military airfields and some civil airfields and cover a period ranging from 3 hours to 30 hours.
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 considerably fewer TAF locations than there are airports for which METARs are available. TAFs can be more accurate than
numerical weather forecasts
, since they take into account local, small-scale, geographic effects.
Today, according to the advancement of technology in civil aviation, the TAF is sent as
IWXXM
model.
[3]
In the United States, the weather forecasters responsible for the TAFs in their respective areas are located within one of the
122 Weather Forecast Offices
operated by the United States'
National Weather Service
. In contrast, a
trend type forecast
(TTF), which is similar to a TAF, is always produced by a person on-site where the TTF applies. In the United Kingdom, most TAFs for 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.
Code
[
edit
]
This TAF example of a 30-hour TAF was 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
FM060600 25010KT 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
aerodrome
forecast.
- KXYZ
indicates the airport to which the forecast applies (
ICAO airport code
).
- 051730Z
indicates that the report was issued on the 5th of the month at 1730
UTC
(also known as Zulu, hence the
Z
).
- 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 contain the initial forecast conditions. Variations of the codes used for various weather conditions are many.
[4]
- 31008KT
indicates that the wind will be from 310° true at 8
knots
(9 mph; 4 m/s).
- 3SM -SHRA BKN020
indicates that visibility will be 3 statute miles (5 km) 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 (600 m) above ground level (AGL).
Each line beginning with
FM
indicates a rapid change in the weather over a period of less than an hour.
- FM052300
indicates the next period lasts from (
FM
) the 5th at 2300 UTC to the 6th at 0600 UTC (the effective time on the next
FM
line). The remainder of the line has similar formatting to the other forecast lines:
30006KT
wind from 300° at 6 knots (11 km/h; 6.9 mph),
5SM
visibility 5 statute miles (8 km),
-SHRA
light rain showers,
OVC030
overcast
at 3,000 feet (900 m).
- PROB30
indicates a 30% probability of the following temporary conditions on the 6th between 0400 UTC and 0600 UTC:
VRB20G35KT
wind of variable direction at 20 knots (35 km/h; 25 mph) with gusts up to 35 knots (65 km/h; 40 mph),
1SM
visibility 1 statute mile (1.6 km),
TSRA
thunderstorms and rain,
BKN015CB
broken
cumulonimbus
clouds at 1,500 feet (450 m).
- FM060600
indicates that the next period lasts from the 6th at 0600 UTC until 2400 UTC (the end of the forecast period, as there is no following
FM
):
25010KT
wind from 250° at 10 knots (20 km/h; 10 mph),
4SM
visibility 4 statute miles (6.5 km),
-SHRA
light rain showers,
OVC050
overcast at 5,000 feet (1,500 m).
- TEMPO
means that these conditions are temporarily replaced, for periods up to 50% of the time, between 0800 UTC and 1100 UTC with:
2SM
visibility 2 statute miles (3 km),
-SHRA
light rain showers,
OVC030
overcast at 3,000 feet (900 m). (The wind speed remains the same, as it is not mentioned.)
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.
See also
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]
References
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]
External links
[
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]