A TAF for the destination airport includes the group: 'TEMPO 1416 3SM -RA BR.' How should a CFII explain this group to an instrument student?
- AConditions with a stated probability of occurring sometime between 1400Z and 1600Z
- BA permanent change in conditions expected to begin at 1400Z and last until 1600Z
- CA gradual, permanent change in visibility and weather taking effect over the 1400Z-1600Z period
- DTemporary, fluctuating conditions of 3 statute miles visibility with light rain and mist, expected between 1400Z and 1600Z, with each occurrence generally lasting less than an hour
Show answer & explanationAnswer & explanation
Correct answer: D. Temporary, fluctuating conditions of 3 statute miles visibility with light rain and mist, expected between 1400Z and 1600Z, with each occurrence generally lasting less than an hour
TEMPO indicates temporary, fluctuating conditions expected to occur during the stated time period, with each occurrence expected to last less than one hour and, in the aggregate, less than half of the period. It does not represent a permanent or gradual change.
Why the other options are wrong
- A. Probability language uses 'PROBxx', not 'TEMPO'.
- B. A permanent change is denoted by 'FM' (from), not 'TEMPO'.
- C. A gradual change is denoted by 'BECMG', not 'TEMPO'.
TAF Change Groups
TAF change indicators describe how forecast conditions evolve: FM for rapid/permanent change, BECMG for gradual change, TEMPO for temporary fluctuations, and PROB30/PROB40 for probability of occurrence.
- FM: rapid, significant, permanent change at a specific time
- BECMG: gradual transition over a time range
- TEMPO: temporary conditions, each episode <1 hour, aggregate <half the period
- PROB30/40: probability (30% or 40%) of the described conditions occurring
Memory trick: FM=Full switch, BECMG=Becoming slowly, TEMPO=Temporary blips, PROB=Probably maybe