FAA Flight Instructor Airplane (FIA)Weather and Weather ServicesMedium
A TAF for an airport includes the group 'TEMPO 1416 1/2SM FG'. How should a pilot interpret this element of the forecast?
- AFog with 1/2SM visibility is expected to occur temporarily, for less than an hour at a time, within the 1400Z–1600Z period
- BA gradual and permanent change to 1/2SM visibility in fog is expected between 1400Z and 1600Z
- CThere is only a 30% probability that fog will occur during the period
- DFog will begin abruptly at 1400Z and continue without change through 1600Z
Show answer & explanationAnswer & explanation
Correct answer: A. Fog with 1/2SM visibility is expected to occur temporarily, for less than an hour at a time, within the 1400Z–1600Z period
TEMPO indicates temporary, fluctuating conditions expected to last less than one hour at a time and occur in less than half of the period. It differs from BECMG (gradual permanent change) and FM (rapid change to new conditions).
Why the other options are wrong
- B. Describes BECMG, not TEMPO.
- C. Confuses TEMPO with the PROB30 probability group.
- D. Describes an FM (from) group, which indicates a rapid, sustained change.
TAF Change Indicators
TAFs use FM, BECMG, TEMPO, and PROB to describe how and when forecast conditions change during the valid period.
- FM = rapid change, all conditions replaced from that time
- BECMG = gradual change over a time range
- TEMPO = temporary fluctuations lasting <1 hour at a time
- PROB30/PROB40 = probability of occurrence, not used with TEMPO for thunderstorms/precip in the same way
Memory trick: TEMPO is a temporary guest — in and out within the hour.