The date/time group for a METAR or SPECI report is appended with what letter?

In a METAR or SPECI report, the date/time group is always followed by the letter "Z," which indicates that the times are expressed in Coordinated Universal Time (UTC). This is important because it standardizes the reporting of weather conditions across different time zones and regions, ensuring that aviation and meteorological professionals can accurately interpret and use the data regardless of their local time zone. The "Z" stands for "Zulu," which is the military designation for UTC.

Using "Z" helps avoid confusion that could arise from using local times, particularly in global contexts where reports may be issued from areas that are several hours apart. The other options do not signify the time format used in METAR or SPECI reports, making "Z" the definitive choice for indicating the date/time is in UTC.