FAA Aircraft Dispatcher (ADX)MeteorologyMedium
A TAF for an arrival airport contains the group 'TEMPO 1014 1/2SM FG'. How should a dispatcher interpret this forecast group?
- AThere is a 30 percent probability that fog will reduce visibility to 1/2SM sometime between 1000Z and 1400Z
- BVisibility will gradually deteriorate to 1/2SM in fog over the period from 1000Z to 1400Z
- CFog reducing visibility to 1/2SM is expected temporarily between 1000Z and 1400Z, for less than half of that period
- DA permanent change to 1/2SM visibility in fog is expected to begin at 1000Z
Show answer & explanationAnswer & explanation
Correct answer: C. Fog reducing visibility to 1/2SM is expected temporarily between 1000Z and 1400Z, for less than half of that period
TEMPO indicates temporary, fluctuating conditions expected to occur for less than half of the indicated time period (1000Z-1400Z in this case), with the specified conditions (1/2SM visibility in fog) expected intermittently rather than continuously.
Why the other options are wrong
- A. A probabilistic forecast uses PROB30 or PROB40, not TEMPO, which is a deterministic temporary condition.
- B. A gradual change is indicated by BECMG, not TEMPO.
- D. A permanent change would be indicated by an FM (from) group, not TEMPO.
TAF Change Indicator: TEMPO
A TAF change group indicating temporary, fluctuating weather conditions expected to occur for less than half of the specified time period.
- Followed by a time range (e.g., 1014 = 1000Z to 1400Z)
- Conditions are intermittent, not continuous, during that window
- Distinct from BECMG (gradual permanent change) and FM (rapid permanent change)
Memory trick: TEMPO = 'temporary tease' — the weather flickers in and out, less than half the time.