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15 MAR 07
Federal Aviation Administration Nineteenth Edition
30.4 Aerodrome Forecast (TAF). A concise statement
of the expected meteorological conditions at an
airport during a specified period (usually 24 hours).
TAFs use the same codes as METAR weather reports.
They are scheduled four times daily for 24-hour
periods beginning at 0000Z, 0600Z, 1200Z, and
1800Z. TAFs are issued in the following format:
Type of Report / ICAO Station Identifier / Date
and Time of Origin / Valid Period Date and
Time / Forecast Meteorological Conditions
NOTEThe
“/” above and in the following descriptions are for
separation purposes in this publication and do not appear
in the actual TAFs.
30.4.1 Explanation of TAF elements
30.4.1.1 Type of Report. There are two types of
TAF issuances, a routine forecast issuance (TAF) and
an amended forecast (TAF AMD). An amended TAF
is issued when the current TAF no longer adequately
describes the on-going weather or the forecaster feels
the TAF is not representative of the current or
expected weather. Corrected (COR) or delayed
(RTD) TAFs are identified only in the communications
header which precedes the actual forecasts.
30.4.1.2 ICAO Station Identifier. The TAF code
uses ICAO 4-letter location identifiers as described
in the METAR section.
30.4.1.3 Date and Time of Origin. This element is
the date and time the forecast is actually prepared.
The format is a two-digit date and four-digit time
followed, without a space, by the letter “Z.”
30.4.1.4 Valid Period Date and Time. The UTC
valid period of the forecast is a two-digit date
followed by the two-digit beginning hour and
two-digit ending hour. In the case of an amended
forecast, or a forecast which is corrected or delayed,
the valid period may be for less than 24 hours. Where
an airport or terminal operates on a part-time basis
(less than 24 hours/day), the TAFs issued for those
locations will have the abbreviated statement “NIL
AMD SKED AFT (closing time) Z” added to the end
of the forecasts. For the TAFs issued while these
locations are closed, the word “NIL” will appear in
place of the forecast text. A delayed (RTD) forecast
will then be issued for these locations after two
complete observations are received.
30.4.1.5 Forecast Meteorological Conditions.
This is the body of the TAF. The basic format is:
Wind / Visibility / Weather / Sky Condition /
Optional Data (Wind Shear)
The wind, visibility, and sky condition elements are
always included in the initial time group of the
forecast. Weather is included only if significant to
aviation. If a significant, lasting change in any of the
elements is expected during the valid period, a new
time period with the changes is included. It should be
noted that with the exception of an “FM” group, the
new time period will include only those elements
which are expected to change; i.e., if a lowering of the
visibility is expected but the wind is expected to
remain the same, the new time period reflecting the
lower visibility would not include a forecast wind.
The forecast wind would remain the same as in the
previous time period.
Any temporary conditions expected during a specific
time period are included with that time period. The
following describes the elements in the above format.
a) Wind. This five (or six) digit group includes
the expected wind direction (first 3 digits) and speed
(last 2 digits or 3 digits if 100 knots or greater). The
contraction “KT” follows to denote the units of wind
speed. Wind gusts are noted by the letter “G”
appended to the wind speed followed by the highest
expected gust.
NOTEA
variable wind direction is noted by “VRB” where the
three digit direction usually appears. A calm wind (3 knots
or less) is forecast as “00000KT.”
EXAMPLE-
18010KT - wind one eight zero at one zero (wind is blowing
from 180 at 10 knots).
35012G20KT - wind three five zero at one two gust two
zero
b) Visibility. The expected prevailing visibility
up to and including 6 miles is forecast in statute miles,
including fractions of miles, followed by “SM” to
note the units of measure. Expected visibilities
greater than 6 miles are forecast as P6SM (Plus
sixstatute miles).
EXAMPLE-
1/2SM . . . . . . . . visibility one-half
4SM . . . . . . . . . visibility four
P6SM . . . . . . . . visibility more than six
30 AUG 07
AIP
United States of America
中国航空网 www.aero.cn
航空翻译 www.aviation.cn
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