AIM
4/20/23
7
−
1
−
78
Meteorology
EXAMPLE
−
FM210100 14010KT P6SM SKC
−
“after 0100Z on the 21st, wind one four zero at one zero, visibility more than six, sky
clear.”
2.
Becoming (BECMG) group. The BECMG group is used when a gradual change in conditions is expected
over a longer time period, usually two hours. The time period when the change is expected is two four
−
digit
groups separated by a “/”, with the beginning date and hour, and ending date and hour of the change period which
follows the BECMG indicator. The gradual change will occur at an unspecified time within this time period. Only
the changing forecast meteorological conditions are included in BECMG groups. The omitted conditions are
carried over from the previous time group.
NOTE
−
The NWS does not use BECMG in the TAF.
EXAMPLE
−
OVC012 BECMG 0114/0116 BKN020
−
“ceiling one thousand two hundred overcast. Then a gradual change to ceiling two
thousand broken between 1400Z on the 1st and 1600Z on the 1st.”
3.
Temporary (TEMPO) group. The TEMPO group is used for any conditions in wind, visibility, weather,
or sky condition which are expected to last for generally less than an hour at a time (occasional), and are expected
to occur during less than half the time period. The TEMPO indicator is followed by two four
−
digit groups
separated by a “/”. The first four digit group gives the beginning date and hour, and the second four digit group
gives the ending date and hour of the time period during which the temporary conditions are expected. Only the
changing forecast meteorological conditions are included in TEMPO groups. The omitted conditions are carried
over from the previous time group.
EXAMPLE
−
1.
SCT030 TEMPO 0519/0523 BKN030
−
“three thousand scattered with occasional ceilings three thousand broken
between 1900Z on the 5th and 2300Z on the 5th.”
2.
4SM HZ TEMPO 1900/1906 2SM BR HZ
−
“visibility four in haze with occasional visibility two in mist and haze between
0000Z on the 19th and 0600Z on the 19th.”