FAA Private Pilot Airplane (PAR)Weather Theory and ServicesMedium
A TAF for KABC includes the group 'BECMG 1418/1420 3SM BR'. How should a pilot interpret this forecast group?
- AA gradual change to 3SM visibility in mist is expected to occur between 1418Z and 1420Z
- BA temporary, short-lived change to 3SM visibility in mist will occur suddenly at 1418Z
- CConditions will probably reach 3SM visibility in mist with a 30 percent chance
- DVisibility will average 3SM in mist for the entire period from 1418Z to 1420Z
Show answer & explanationAnswer & explanation
Correct answer: A. A gradual change to 3SM visibility in mist is expected to occur between 1418Z and 1420Z
BECMG (becoming) indicates a gradual change expected to occur within the specified time window, here between 1418Z and 1420Z, transitioning to visibility of 3 statute miles in mist (BR).
Why the other options are wrong
- B. TEMPO, not BECMG, indicates temporary short-lived fluctuations.
- C. PROB30 indicates probability, which is a different forecast group than BECMG.
- D. BECMG describes a transition, not a steady average condition throughout the period.
TAF BECMG Group
BECMG indicates a gradual change in conditions expected to occur within a specified time window in the forecast, after which the new conditions are expected to persist.
- BECMG differs from TEMPO (temporary) and FM (rapid/abrupt change)
- The two times given represent the window over which the change occurs
- New conditions after BECMG persist until the next change group
Memory trick: BECMG = 'becoming' gradually, like a slow sunrise, not a light switch