About Weather Watch Radar Images

What The Radar Sees

Weather Watch radars are very effective tools for the detection of rain. Bureau forecasters can interpret the patterns and intensity of the radar images to provide warnings of major weather events such as severe thunderstorms, tropical cyclones and areas of heavy rainfall.

Note that the radar does not "see" clouds, as cloud droplets are too small, but does see the rainfall which those clouds produce. These areas of rain "seen" by the radar are often called radar echoes. The radar may sometimes detect echoes from aircraft, areas of smoke/ash from large fires, swarms of insects, flocks of birds or even the ground or sea surface, when unusual atmospheric conditions bend the radar beam back down to the surface. As a result, there may be patterns on the radar images that do not represent falling rain.

Approximate Rainfall Rates

Radar Features to Watch For

Rain Bands (Example)
Radar echoes from widespread rain (e.g. from a frontal rain band) are usually extensive and fairly uniform in intensity, with ill-defined edges. The estimated rainfall intensity usually appears as light to medium because of the smaller raindrop size produced in such rain bands.

Showers from Cumulus Clouds (Example)
Radar echoes from showers falling from cumulus (tall bubbly clouds) appear as sharp-edged cells scattered around the radar display. The estimated rainfall intensity can be medium to heavy owing to the high rainfall rates from such clouds.

Heavy Precipitation from Thunderstorms (Example)
Radar echoes from the rain and hail produced in thunderstorms are very sharp-edged cells with intense cores indicating heavy rainfall. Hailstones produce particularly intense echoes because of their large size. Thunderstorm precipitation cells can appear as isolated cells or in clusters or lines. Each cell tends to last for 30 minutes or more. Fast moving cells, rapidly growing cells, a bow in the direction of movement of a line of cells and/or a long-lived cell moving in a markedly different direction to others may indicate the potential for severe weather (large hail, damaging winds and/or very heavy rain). Also a very slow moving cell or the repeated passage of a number of cells over a particular location could indicate potential for flash flooding.
Example: Radar Image loop of Melbourne Thunderstorm, 2/12/03

Tropical Cyclones
Tropical cyclones produce widespread heavy rain. The tendency for the rain bands, often with embedded cells, to spiral around the rain-free cyclone 'eye' produces a characteristic radar pattern. Of course, many tropical cyclones are so extensive that they are rarely seen entirely by a single radar. Nevertheless, identification of the 'eye' on radar is very useful in identifying the tropical cyclone centre and its movement.
Example: Radar Image loop of Tropical Cyclone Larry, 19/03/06 (5MB. Opens in new window)

More Information About Radars

Australian Weather Watch Radar
Interpreting Radar Images - Frequently Asked Questions
About Radar Loops
Australian Weather Watch Radar Network
How Radar Works