When in a TAF report, there is written "TEMPO 1923", does it mean a weather changer for the whole 4 hours?

Question

Or does it mean that maybe, the weather changes for one hour, between 19 and 23?

Answer 1

"The change-indicator group TEMPO GGGeGe is used to indicate temporary fluctuations to forecast meteorological conditions which are expected to:



• Have a high percentage (greater than 50%) probability of occurrence,

• Last for one hour or less in each instance and,

• In the aggregate, cover less than half of the period GG to GeGe"

So, it will not last for the entire 4 hours, but will fluctuate during that 4 hour period for less than an hour at a time and no more than two hours total.

Answer 2

it means the weather will change at a regular or irregular rate for a time period of 1hr or less between the validity of the tempo and each period in aggregate will be less than half of the validity of the tempo.

Answer 3

I read TAF about twice a week (I own my aircraft and can fly whenever I want! :-) and when I read TEMPO 1923, I understand it as what follows will be for the period indicated; also, for four hours. For example, morning fog in a high pressure will read TEMPO 0509 BCGF.