IRFP-01
Metro Review
7. Automated Weather Observation System (AWOS)
a. AWOS is a real-time system consisting of various sensors, a
processor, a computer-generated voice subsystem, and
transmitter to broadcast local minute-by-minute weather
directly to the aircraft
(1) AWOS observations derived from an automated system
will include the prefix “AWOS”
(2) Some AWOS locations will be augmented by certified
observers who will provide weather and obstruction to
visibility information in the remarks of the report when the
reported visibility is less than 3 miles. Augmentation is
identified as “OBSERVER WEATHER”
(3) The reported visibility is derived from a sensor near the
touchdown of the primary instrument runway
NOTE: The AWOS visibility is reported as a runway
visibility range and may differ from the prevailing visibility.
(4) The reported sky condition/ceiling is derived from the
ceilometer located next to the visibility sensor and may
differ from the observed sky condition, because the AWOS
is totally dependent on clouds over the sensor site
b. There are four operational levels of AWOS
(1) AWOS-A - reports only altimeter setting
(2) AWOS-1 - reports altimeter setting, wind data,
temperature, dew point, and density altitude
(3) AWOS-2 - reports information in AWOS-1 plus visibility
(4) AWOS-3 - reports information in AWOS-2 plus cloud and
ceiling data
(5) AWOS information is transmitted over a discrete frequency
or the voice portion of a local NAVAID
NOTE: The system transmits a 20- to 30-second weather
message each minute. The messages are updated each
minute and are receivable within 25 nm of the AWOS site,
at or above 3,000 ft AGL.
c.
AWOS broadcasts phraseology generally follows that used in
other weather broadcasts. The following are explanations of
exceptions:
(1) The word “TEST” is added when the system is not in
commissioned status
(8-97) Original
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