AIM

4/3/14

7−1−30

Meteorology

(b)

National communications networks.

(c)

Computer-generated voice (available

through FAA radio broadcast to pilots, and dial-in

telephone line).

NOTE

−

Wind direction broadcast over FAA radios is in reference
to magnetic north.

4.

An ASOS/AWOS/AWSS report without

human intervention will contain only that weather

data capable of being reported automatically. The

modifier for this METAR report is “AUTO.” When

an observer augments or backs−up an ASOS/AWOS/

AWSS site, the “AUTO” modifier disappears.

5.

There are two types of automated stations,

AO1 for automated weather reporting stations

without a precipitation discriminator, and AO2 for

automated stations with a precipitation discriminator.

As appropriate, “AO1” and “AO2” must appear in

remarks. (A precipitation discriminator can deter-

mine the difference between liquid and

frozen/freezing precipitation).

NOTE

−

To decode an ASOS

/AWSS

 report, refer to FIG 7

−1−9 and

FIG 7

−1−10.

REFERENCE

−

A complete explanation of METAR terminology is located in AIM,
Paragraph 7

−1−30, Key to Aerodrome Forecast (TAF) and Aviation

Routine Weather Report (METAR).