FAA Airline Transport Pilot (ATM)Meteorology and Weather ServicesMedium
A pilot reviewing a TAF for the destination airport sees the group 'FM152000' within the forecast. What does this group indicate?
- AThere is a 20 percent probability of the forecast conditions occurring
- BA temporary fluctuation in conditions is expected sometime between 1500Z and 2000Z
- CThe forecast is valid only from 1500Z through 2000Z on the 15th
- DConditions after 2000Z on the 15th are expected to change fairly rapidly, usually within an hour
Show answer & explanationAnswer & explanation
Correct answer: D. Conditions after 2000Z on the 15th are expected to change fairly rapidly, usually within an hour
The 'FM' group in a TAF indicates a rapid and significant change in prevailing conditions expected to begin at the specified time (here, 2000Z on the 15th), typically occurring within one hour. The entirely new set of conditions following FM replaces the previous forecast group.
Why the other options are wrong
- A. Probability groups use 'PROB' followed by a percentage, not 'FM.'
- B. Temporary fluctuations are indicated by 'TEMPO,' not 'FM.'
- C. FM does not bound a validity window; it marks the start of a new, complete forecast group.
TAF Change Group: FM
An indicator in a Terminal Aerodrome Forecast marking a rapid, significant change in conditions beginning at a specific time, replacing prior forecast conditions.
- FM is followed by day/hour/minute (DDHHMM) in UTC
- Change occurs in about an hour or less
- Represents a full replacement, not a temporary or probable condition
Memory trick: FM = 'From now on, things change fast.'