# What does AO2A in the remarks of a METAR mean?

I am familiar with AO2 in the METAR remarks as described in this answer, which means the station is automated and has a precipitation discriminator. I have noticed sometimes there is AO2A in the remarks now as in this METAR:

KBAD 171406Z 17012KT 10SM OVC004 18/17 A3002 RMK AO2A SLP168

How is AO2A different from AO2? I assume it is probably some additional capability.

## 1 Answer

AO2 Automated station without manual augmentation
AO2A Automated station with manual augmentation.

That means this is an automated station but some elements have been added manually.

15.13.4 Supplementary remarks may be included in observations from US stations following the identifier group RMK. These data are intended as national interest only and are equivalent to Section 5 of FM 12 SYNOP.

Observations from automated stations shall have one of the following contractions as the first entry following RMK: AO2 Automated station without manual augmentation; AO2A Automated station with manual augmentation.

Source WMO Manual on codes.