What does a METAR report with an Auto modifier mean?

• A. Auto report with observer backup.
• B. Purely an auto report without an observer backup or augmentation.
• C. Auto report generated with manual override.
• D. Auto report with weather radar augmentation.

Answer: (B)

Automated weather reporting is the concept here. When a METAR includes the Auto modifier, it means the entire observation was produced by automated equipment at the station (ASOS/AWOS) with no on-site human observer involved in taking or verifying the observation. In other words, there is no observer backup or manual augmentation contributing to that report.

That’s why the correct interpretation is that it’s a purely automatic METAR. The other options imply human involvement or augmentation (backup, manual override, radar augmentation), which doesn’t fit the meaning of the Auto modifier in METARs.