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Interpreting Data
What do pressure charts show?
Pressure charts, also known as synoptic charts, show the movement of high and low pressure systems across the country. The solid white lines are called isobars, and these connect points of constant pressure. In the Southern Hemisphere, winds blow clockwise around low pressure systems and anticlockwise around high pressure systems. Generally, the closer the isobars are together, the stronger the winds will be.
As a very rough rule, high pressure systems bring settled, stable weather, while low pressure systems bring rain or storms. However, there are many exceptions to these rules, with highs often causing gloomy, overcast conditions. Also note that the pressure charts are only showing what is going on at the surface. A very large part of weather forecasting is concerned with what is happening in the upper levels above the surface.
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A very wet weekend for southeast Qld, northeast NSW
11:48 AEST A prolonged rainfall event is set to bring large totals to parts of NSW and Qld from Saturday, with possible heavy falls and flooding. A low-pressure system in the Coral Sea, a deepening coastal trough and persistent easterlies will bring moisture-laden air into southeast Qld and northeast NSW will bring days of rainfall to the region. While there is not a drop of rain on the radar over southeast Qld and Northeast NSW on Friday morning, the mass of cloud associated with a low in the Coral Sea will enhance rainfall over the weekend.
- 10:07 AEST Southerly surges across the southeast
- 13:20 AEST Generation gone with the wind
- 11:29 AEST Devilishly dry in Tasmania
- 16:41 AEST Dubai deluge: a year's rainfall in a day
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