Marine Glossary

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southerly buster

A sudden shift of wind to the southeast in the south and southeast parts of Australia, especially frequent on the coast of New South Wales near Sydney in summer. It occurs in the rear of a trough of low pressure which is followed by the rapid advance of an anticyclone from West Australia. Also called just buster or burster.

After some days of hot, dry northerly wind (brickfielder), heavy cumulus clouds approach from the south, the wind drops to calm and then sets in suddenly from the south, sometimes reaching gale force. Temperature at Sydney has fallen from 100° F to 64° F in thirty minutes.

The average summer frequency of southerly busters at Sydney is 32. Similar winds are experienced in the east of South Africa, especially near Durban.

==========here is another defintion

The NSW Southerly Buster is an intense pre-frontal squall leading a cold front moving up from the Southern Ocean and occurring maybe 30 times per year, with about 10 major events usually in spring and summer. The phenomenon is a shallow density current 20 – 50 nm wide centred on the coast and surging northward at 15 knots with 30 – 60 knot gusts. The temperature may fall 10 °C – 15 °C over a few minutes and there may be extreme low level turbulence. A spectacular roll cloud may form above the nose but usually there is little cloud and consequently little warning.

A prime cause is the interaction of a shallow cold front with the blocking mountain range which parallels the coast, and frictional differences over land and sea uncouple the flow. Other phenomena lead to intensification of the temperature gradient between the warm air mass and the cold density current. e.g. hot north-westerly or warm dry foehn wind preceding the squall. Severe thunderstorm activity may result from the forced lifting of warm, humid air.