The number following WHFT in a METAR indicates what?

In a METAR report, WHFT refers to a wind shift that has commenced at a specified time. The number that follows WHFT indicates the time, in hours and minutes, when the wind shift began. This is crucial information for pilots and meteorologists as it helps them understand recent changes in wind direction and speed, which can significantly affect flight operations, especially during takeoff and landing phases.

Knowing the specific start time of a wind shift allows for better situational awareness and more accurate flight planning. For example, if a significant wind shift occurs that could impact landing approaches or takeoff trajectories, having the exact time helps assess how long the current conditions have existed and what changes might be expected in the near future.

The other answers do not pertain to the function or meaning of WHFT in this context. The maximum wind speed, elevation of the winds, or duration of the shift are not indicated by the number following WHFT. This concentration on the onset timing of the wind shift is what makes the correct context relevant for aviation safety and operational planning.