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How to read the automatic weather station reports

Automatic weather stations (AWS) provide frequent near continuous reports, with AWN showing the main ones every 30 minutes. In addition, we show special reports whenever certain conditions are met, such as sudden temperature falls or rises, heavy rainfall or changes in wind direction or strength. The reports given on AWN include the full Bureau of Meteorology network (which have a six-digit site Id number in the left column) and a selection from private networks (where the last three characters of the site Id number are letters). Reports from non-Bureau sources may not meet Bureau standards.

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 used to be made by a human observer using his or her eyes. They are critical observations for aviation. Since 1996 the Bureau has progressively introduced automatic visibility meters and ceilometers which automatically measure cloud amounts and bases to about 130 of the total 650 AWSs in Australia. While the type of weather that is occurring at fully automatic AWSs is not reported, it can usually be deduced from other readings, e.g. if visibility is below 1000m then there is fog, and if there is rain in the "past 10 mins" column it is likely to be raining.

At some of the busiest airports, a Bureau staff member still feeds two lots of additional information into the AWS data before it is sent off to the Bureau: the types of clouds associated with each level and the types of weather occurring at the airport. In our tables, this human data is marked with an asterisk (*) in the visibility column while sensor data is not.

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 base of 1260m or 1.26km - in this case no cloud type shown so it is a sensor observation. The codes are:

Amount of cloud
Type of cloud

FE = few (1 or 2 oktas)
SC = scattered (3 or 4 oktas)
BR = broken (5 to 7 oktas)
OV = overcast

ac = Altocumulus
as = Altostratus
cb = Cumulonimbus
cc = Cirrocumulus
ci = Cirrus
cs = Cirrostratus
cu = Cumulus
ns = nimbostratus
sc = stratocumulus
st = stratus
tc = towering cumulus

Weather: At busy airports manned by Bureau staff, the type of weather occurring at the time of observation is given in the code below. 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:


di = distant
lt = light
md = moderate
hv = heavy


Sh = shallow (e.g. fog)
Bk = broken (or in patches)
Pa = partial (covering part of)
Dr = drifting (e.g. sand, snow)
Bl = blowing (e.g. dust)
Sh = showers (e.g. rain, snow)
Ts = thunderstorm
Fz = freezing (e.g. fog, rain)

DD = dust devils
DS = duststorm
DU = dust
DZ = drizzle
FG = fog
FN = funnel cloud
HL = hail
HZ = haze
IC = ice crystals
IP = ice pellets
MI = mist
RA = rain
SA = sand
SG = snow grains
SM = smoke
SN = snow
SQ = squalls
SS = sandstorm
VA = volcanic ash