AWOS II - Same as AWOS I + visibility, variable visibility, precipitation, day/night
AWOS III - Same as AWOS II + cloud height and sky condition
AWOS information can be transmitted via VHF radio, NBD, or VOR ensuring that pilots
on approach have up-to-date airport weather conditions. Transmissions can be
continuous or three-minute broadcasts triggered by three clicks of a pilot s microphone
on the AWOS broadcast frequency. Information is also available by telephone so that
conditions can be obtained from any location.
ASOS is the primary surface weather observing system in the United States and at
selected naval overseas sites. ASOS is designed to support aviation operations and
weather forecast activities. This system continuously samples and measures ambient
environment and provides a variety of observations, including 1- and 5-minute
observations, METARs, and SPECI products. The ASOS consists of three main
components and a video tower display.
Two types of automated ASOS stations exist:
AO1 is for automated weather reporting stations without a precipitation
AO2 is for automated stations with a precipitation discriminator.
A precipitation discriminator can determine the difference
between liquid and frozen (or freezing) precipitation.
ASOS information can be transmitted over a discrete VHF radio frequency or the voice
portion of a local NAVAID. An aircraft should be able to receive these transmissions up
to a maximum of 25 nautical miles (nm) from the ASOS site and a maximum altitude of
10,000 feet AGL.
WEATHER FORECASTS, ADVISORIES, AND WARNINGS
Airfield operators, pilots, and air traffic control personnel cannot plan flight operations or
workloads on existing weather conditions only; they must also rely on predicted weather
conditions (forecasts). The following discussion on forecasts, advisories, pilot reports,
and warnings will inform you of what is available to assist you in your planning.