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AIM 

6/17/21 

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.” 

7

1

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Meteorology