FAA Commercial Pilot Airplane (CAX)WeatherEasy
A pilot is conducting a preflight briefing and notes a TAF for their destination airport that includes 'PROB30 1800/1802 TSRA'. What does this indicate for the forecast period?
- AA 30% chance of temporary scattered thunderstorms and rain.
- BA 30% chance of isolated rain showers after 1800Z.
- CProbability of 30 knots wind with thunderstorms and rain at 1800Z.
- DA 30% chance of thunderstorms with rain between 1800Z and 1802Z.
Show answer & explanationAnswer & explanation
Correct answer: D. A 30% chance of thunderstorms with rain between 1800Z and 1802Z.
In a TAF, 'PROB30' indicates a 30% probability of the specified weather occurring. '1800/1802' is the time period (1800Z to 1802Z), and 'TSRA' stands for thunderstorms with rain. Therefore, it forecasts a 30% chance of thunderstorms with rain during that specific two-hour window.
Why the other options are wrong
- A. Incorrect. 'PROB30' is a specific probability, not a temporary condition, and 'TSRA' is not necessarily 'scattered'.
- B. Incorrect. 'TSRA' is thunderstorms with rain, not just isolated rain showers, and the time period is specific.
- C. Incorrect. 'PROB30' is probability, not wind speed, and the wind would be reported separately.
TAF PROB30/40
In a TAF (Terminal Aerodrome Forecast), 'PROB30' or 'PROB40' indicates a 30% or 40% probability, respectively, of the specified weather phenomenon occurring during the indicated time period.
- PROB30 = 30% probability.
- PROB40 = 40% probability.
- Indicates a low to moderate chance of occurrence.
- Weather specified is expected to occur, but with uncertainty.
- Used for significant weather like thunderstorms, precipitation, or low visibility.
Memory trick: PROB: Percentage of Possibility, Precisely Pointed.