What information is omitted if RVR is not observed on the METAR report?

In a METAR report, when the Runway Visual Range (RVR) is not observed, it is specifically the group that indicates the RVR value along with the preceding space that is omitted. The RVR is a crucial component for assessing visibility specifically for runway operations, and when it is not available, the METAR report will simply exclude that group entirely, rather than providing an alternative or placeholder.

Including this group is important, as it provides information on how far a pilot can see down the runway, which is vital for takeoff and landing decision-making. If the RVR is not measured or is unavailable, the report will remain devoid of that specific piece of information, thus leaving out both the group related to RVR and the preceding space that would have been present if RVR were available.

In contrast, other elements such as wind information, temperature data, and runway designators are foundational pieces of a METAR and would not be omitted due to RVR observations.