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Understanding Terminal Aerodrome Forecasts

2016 March 27

Terminal Aerodrome Forecasts (TAFs) are detailed, accurate weather forecasts which describe the expected weather conditions at an airport, usually for a 24 hour period. Amateur astronomers, outdoor enthusiasts, and others can use TAFs to get a good idea of what the weather will be like at a given location. The first step is to find the nearest sizable airport [1] or military airfield. If the area is far away from any aerodromes, select the three or four air facilities so that they form a triangle or square with the area of interest near the center.

Next, look up the four letter codes for the selected airport(s). A list of selected aerodrome identifiers are listed below.

Arizona

Douglas Bisbee International Airport KDUG
Flagstaff Pullman Airport KFLG
Fort Huachuca KFHU
Grand Canyon National Park Airport KGCN
Prescott, Love Field KPRC
Tucson International Airport KTUS
Winslow Municipal Airport KINW
Yuma International Airport KYUM

California

Arcata Airport KACV
Bakersfield, Meadows Field KBFL
Beale AFB KBAB
Bishop Airport KBIH
Blythe Airport KBLH
China Lake, Naval Air Facility KNID
Barstow-Dagget Airport KDAG
Edwards AFB KEDW
Fresno Air Terminal KFAT
Imperial County Airport KIPL
Lancaster/Fox Field KWJF
Lemoore NAS KNLC
Los Angeles International Airport KLAX
Needles Airport KEED
Palmdale Production Flight Plant KPMD
Palm Springs Regional Airport KPSP
Point Mugu, Naval Air Warfare Center KNTD
San Luis Obispo County-McChesney Field KSBP
Santa Maria Public Airport KSMX
Twenty-Nine Palms, Marine Corps Air-Ground Combat Center KNXP
Vandenberg AFB KVBG

Nevada

Elko Municipal-Harris Field KEKO
Ely Airport KELY
Fallon Naval Air Station KNFL
Las Vegas, McCarran International Airport KLAS
Lovelock, Derby Field KLOL
Mercury, Desert Rock Airport KDRA
Reno Tahoe International Airport KRNO
Tonopah Airport KTPH
Winnemucca Municipal Airport KWMC

Utah

Bryce Canyon Airport KBCE
Cedar City Municipal Airport KCDC
Ogden, Hill AFB KHIF
Ogden, Ogden-Hinckley Airport KOGD
Salt Lake City International Airport KSLC
Vernal Airport KVEL

To find the ID of airports not in the list, click on the following link:

Meteorological Station Information Lookup

Once you have the air facility ID(s), click on the following link to download the most recent TAF(s):

TAF Data Access

TAF Format

You'll notice that the TAF(s) are in a coded form. The format is as follows:

Line 1

[Station ID] [Origin Date/Time] [Valid Period] [Wind] [Horizontal Visibility] [Cloudcover] [Wind Shear]

Following Lines

[Time] [Wind] [Horizontal Visibility] [Cloudcover] [Wind Shear]

Each of the TAF sections are explained in detail below.

Station ID

This is the four character identifier of the air facility.

Origin Date/Time

The date and time when the forecast was completed. The first two digits are the day of the month, followed by the time (in UTC). For example, an origin date/ time of

171155Z

means that the TAF was completed on the 17th at 1155 UTC.

Valid Period

The time period which the TAF covers, usually 24 hours. This consists of a two- digit date followed by a 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 less than 24 hours. Here are some typical entries:

110024 Forecast valid from 00:00 UTC on the 11th until 00:00 UTC on the 12th
091212 Forecast valid from 12:00 UTC on the 9th until 12:00 UTC on the 10th

Wind

The first three characters is the direction, in degrees from magnetic north, from which the wind will be blowing. The next two characters are the wind speed. Next is KT, the abbreviation for knots. If the wind is gusting, the abbreviation G is present followed by the maximum wind speed of the gusts. Here are some typical wind entries:

00000KT No wind
23012KT Wind direction 230 degrees. Wind speed 12 knots
33015G25KT Wind direction 330 degrees. Wind speed 15 knots with gusts to 25 knots
VRB03KT Wind direction variable. Wind speed 3 knots

Horizontal Visibility

This is a measure of how far features can be seen along the ground. U.S. civilan airports express visibility in statute miles; U.S. military facilities express it in meters. The following are some typical horizontal visibility entries:

1/2SMVisibility 1/2 statute mile
2SMVisibility 2 statute miles
P6SMVisibility greater than 6 statute miles
0800Visibility 800 meters
4800Visibility 4,800 meters
9999Visibility greater than 6,000 meters

Cloudcover

This is the amount of cloudcover (SKC, FEW, SCT, BKN, or OVC) followed by the height of the clouds given in thousands and hundreds of feet. For example,

SCT005 BKN025CB BKN250

means scattered clouds at 500 feet, broken cumulonimbus clouds at 2,500 feet, and broken clouds at 25,000 feet. Cumulonimbus clouds the only cloud types predicted in TAFs. When the sky is obscured by fog or mist, a VV (vertical visibility) is used followed by the vertical visibility in hundreds of feet.

Wind Shear

This section contains the contraction WS if wind shear is predicted. The WS is followed by the height of the wind shear in hundreds of feet above ground level, the direction (in degrees from magnetic north) from which the wind is expected to blow, and the predicted wind speed in knots. For example,

WS010/18040KT

translates to wind shear at 1,000 feet with a wind direction of 180 degrees and windspeed of 40 knots.

TAF Abbreviations and Symbols

-Light intensity
+Heavy intensity
ACCAltocumulus castellanus clouds
ACSLAltocumulus standing lenticular clouds
APRXApproximately
BBegan
BCPatches
BECMGBecoming. A gradual change in conditions, usually over a period of 2 hours
BKNBroken. Cloudcover 62.5 - 87.5%
BLBlowing
BRMist
CACloud-to-air lightning
CBCumulonimbus clouds
CBMAMCumulonimbus mammatus clouds
CCSLCirrocumulus standing lenticular clouds
CGCloud-to-ground lightning
CIGCeiling
CONSContinuous
CORCorrection to a previously disseminated report
DRLow drifting
DSDust storm
DUWidespread dust
DZDrizzle
EEast, ended
FCFunnel cloud
FEWFew clouds. Cloudcover 12.5 - 25%
FGFog
FMFrom. Used to indicate when a rapid change, usually in less than one hour, in conditions is expected. FM is followed by are four digits which indicate the hour and minute that the change is expected to occur and continues until the next BECMG, FM, or TEMPO or until the end of the forecast.
FRQFrequent
FTFeet
FUSmoke
FZFreezing
GGusts
GRHail
GSSmall hail and/or snow pellets
HZHaze
ICIce crystals, in-cloud lightning
INSInches of mercury
KTKnots
LLeft
LTGLightning
LWRLower
MMinus, less than
MIShallow
NNorth
NENortheast
NSWNo significant weather
NWNorthwest
OCNLOccasional
OHDOverhead
OVCSky overcast. Cloudcover 100%
PGreater than
PEIce pellets
PK WNDPeak wind
PODust/sand whirls (dust devils)
PRPartial
PRESFRPressure falling rapidly
PRESRRPressure rising rapidly
PYSpray
QNHTBD
RRight
RARain
SSouth
SASand
SCSLStratocumumlus standing lenticular clouds
SCTScatterred clouds. Cloudcover 37.5 - 50%
SESoutheast
SFCSurface
SGSnow grains
SHShowers
SKCSky clear
SMStatute miles
SNSnow
SNICRSnow increasing rapidly
SQSqualls
SSSandstorm
SWSouthwest
TCUTowering cumulus clouds
TEMPOTemporary. Used for conditions which are expected to last for less than an hour at a time and are expected to occur less than half the time period. TEMPO is followed by a four-digit group which gives the beginning and ending hour of the period during which the conditions are expected.
TSThunderstorms
VVariable
VAVolcanic ash
VCIn the vicinity
VISVisibility
VRBVariable wind direction with a wind speed of 6 knots or less
VVVertical visibilty
WWest
WNDWind
ZZulu time (same as UTC)

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