Question

When considering alternate aerodromes to select based on the alternate aerodrome minima, what is the difference between PROB and the other two predictions of TEMPO and BECMG in a TAF?

Answer 1

PROB, TEMPO, and BECMG are three different predictions used in a TAF to consider alternate aerodromes. PROB represents a probability forecast, TEMPO indicates temporary conditions, and BECMG indicates a gradual change in conditions.

Step-by-step explanation:

When considering alternate aerodromes to select based on the alternate aerodrome minima in a Terminal Aerodrome Forecast (TAF), there are three different predictions that can be given: PROB, TEMPO, and BECMG.

PROB represents a probability forecast that is used when there is uncertainty about the occurrence of certain weather conditions at the alternate aerodromes. It is expressed as a percentage and indicates the chance of specific conditions (such as visibility or cloud cover) occurring between two specific times.

TEMPO stands for temporary and is used when the forecasted weather conditions are expected to occur for a period of time less than one hour, but more than 30 minutes, during the validity period of the TAF.

BECMG is short for becoming and is used when a gradual change is expected to occur in the weather conditions at the alternate aerodromes. It indicates that the conditions will change, but the exact timing of the change may not be known.