Automatic weather stations (AWS) provide reports at least hourly and often every 30 minutes. In addition, they produce special reports whenever certain conditions are met, such as sudden temperature falls or rises, heavy rainfall or increases in wind strength. All reports for all stations in Australia are given on AWN, and are updated each 15 minutes.

Most of the items reported are pretty obvious, but you may need help with the following columns:

Wind: The first figure given in the sustained or average windspeed over the past 10 minutes. The second is the strongest gust recorded over the past 10 minutes.

Visual observations: Visibility, cloud and weather are known as visual observations because they are usually made by a human observer using his or her eyes. They are critical observations for aviation. At many airports, a Bureau staff member feeds this additional information into the AWS data before it is sent off to the Bureau.

However, many AWSs are now equipped with sensors that allow them to make a good estimate of visibility and cloud cover, while some aspects of the weather can be deduced from the observations. AWSs at smaller airports and locations critical for aviation are being equipped with these sensors. The AWN reports carry both the human and sensor data - human data is *** asterisked.

Visibility: is given in metres, so 7000 = seven thousand metres = 7km.

Cloud cover: Up to three levels or layers of cloud can be reported. For each level, the cloudbase and the amount of sky covered by that layer are given. If it is a human observation, the cloud type is also given. For example, SC 390st BR 900sc tells us there are two cloud layers. The first is SCattered stratus with a cloudbase of 390 metres. The second is BRoken stratocumulus with a base 900m above ground level. A report of SC1260 means scattered cloud with a 1.26km high base - there's no type shown so this must be a sensor observation. The codes are:

Weather: Up to two types of weather can be reported simultaneously, such as fog and rain. Each type of weather can further be broken down by its intensity and character. So mdShRA is moderate showers of rain, diTsRA is distant thunderstorm with rain and hvTsHL is a heavy thunderstorm with hail. Elements may be omitted, such as di//DD (distant dust devils) or lt//RA (light rain). The codes are:

21/06/07