||Code group specifications
||Indicates that the message has been corrected due to some formal mistakes.
||Indicates that the message has been amended due to some substantive modifications.
||Date and time of observation
||The first two numbers indicate the day of a month (26- twenty sixth day), next four numbers indicate the formal time of observation (0500-five zero), letter Z stands for UTC.
||Message day and validity period
||First two numbers indicate the day of a month (26 and 27), next two numbers indicate validity hours.
||Information on surface wind direction and speed
||First three numbers indicate the mean wind direction from true north (360°). In the case of variable wind direction numerical values shall be encoded as VRB when the mean wind speed is less than 3KT unless a thunderstorm passes over the aerodrome. Two next numbers indicate the mean wind speed (05 knots). In the case of wind gusts after letter G a maximum wind gust shall be reported (G20 stands for a wind gust speed of 20 knots). KT stands for “knots”.
||Visibility value is given in metres (for example 5000 meters). Number 9999 indicates the visibility of 10 km or more.
||The type and intensity of weather phenomena
||TAF message reports only of moderate and heavy weather phenomena. Weather phenomena of a weaker intensity is reported only then when visibility is less than 5000 metres. The reason of visibility limitation shall be given.
The following symbols shall be used: when weak intensity of a phenomenon is observed “-“, when heavy “+”. No symbol is applied when moderate phenomenon is observed. Up to three groups reporting phenomena shall be given. To indicate the end of weather phenomena, in a message that is still valid, the abbreviation WX NIL shall apply.
||Cloud amount and cloud height
||Cloud amount shall be given with English code words- FEW, SCT, BKN, OVC.
The height of the cloud base shall be given in numbers and reported in steps of 100 ft (001 stands for 100 ft that is 30 m). No types of clouds are given, except for CB.
||Nil significant clouds
||NSC code is used when:
– the cloud base is not lower than 1500 m (EPKK 1660)
– no CB clouds are expected
– no vertical visibility limitation is expected
– visibility limitation is expected
– and/or significant weather phenomena are expected
||Stands for Ceiling And Visibility OK
||Used when it is expected that the following conditions will apply simultaneously:
– visibility 10 km or more
– no cloud below 1500 metres (for EPKK it is 1660) or below the highest minimum sector altitude, whichever is greater, and no Cumulonimbus
– no significant weather phenomena
||Changes to one or more of the elements of the forecast
||This group shall be used to determine the way and time of occurrence of weather conditions different that these reported in message core part. The following abbreviations are applied:
BECMG – the change of one weather type to other when the time period of the change should normally be less than 2 hours and in any case should not exceed 4 hours; includes information on the changes of weather forecast elements, in case of clouds change it includes all forecasted clouds groups
FM – indicates a significant change of the weather forecast elements occurring at a given time
TEMPO – indicates temporary fluctuations of weather forecast elements which last less than half of the time period
|BECMG 0212/0214 9999 NSW
TEMPO 0212/0221 3000 SHSN BKN020CB
FM021230 0600 FG
||Information on the probability of occurrence of alternative values of forecast elements
||Used in order to indicate the probability of occurrence of alternative values of forecast elements, during a defined period of time. It is combined with the group TEMPO or only with the group that determines the time of occurrence. Only the values 30 and 40 shall be used. Phenomena which rate of probability is higher than 40% is recognized as evident. Phenomena which rate of probability is lower than 30% is not reported.
||PROB30 TEMPO 0212/0221 5000 TSRA BKNO20
PROB40 0203/0206 0500 FG OVC002