Please help me with METAR
 

Greetings Guys recently I have had an Aviation Meteorology exam. During the exam, I encountered a very naughty example of METAR.
I couldn't copy the whole example so I remember only the part related to the question.
081800Z 0600S 6000N R08/0800V1400D BECMG FM1900 2000.
The question was: At 1900Z what would be the visibility?

The answer would be 2000 meters. The last part tells you this:

081800Z 0600S 6000N R08/0800V1400D BECMG FM1900 2000.

Becoming from 1900z - visibility will be 2000m

I presume that would be 2000 in every direction.

That is a :mad: of a question.

The reference document is ICAO Annex 3 Appendix 3.

Based on the information provided the best answer is 6000m which is the prevailing visibility until 1900. The code FM1900 indicates the visibility will start to deteriorate at 1900 and in this case because there is no TL code it means the change to 2000m will be complete at the end of the trend period (by definition, 2 hrs from the time of the METAR).

For the answer to be 2000, the trend would have to be coded either BECMG TL1900 2000, or BECMG AT1900 2000, or BECMG FM(a time) TL1900 2000.

So in this case the visibility is 6000m until 1900 when the deterioration to 2000m will commence.