FIGURE7 A typical weather map
Shading indicates rain fell in the previous 24 hours.
Greater distance between isobars indicates wind is weaker in these regions.
Cold front advancing from west to east — towards southern Australia. Note how the isobars behind it are close together, indicating strong winds.
Darwin
LOW
Townsville
HIGH
High-pressure system. Note
how the isobar is joining points with an atmospheric pressure of 1016 (higher than 1013 average). The cold front that has just passed over Melbourne has brought unsettled, rainy weather behind it. More rainy weather is likely for Melbourne when the cold front coming towards it from the west gets closer.
Brisbane
HIGH
HIGH
Perth
Adelaide
Sydney
LOW
Canberra
Melbourne
LOW
Hobart
0 500 1000 km
1020
Isobar (value in hectopascal)
MELBOURNE
Cold front
Rainfall in previous 24 hours
NOON
Warm front
Trough
Source: MAPgraphics Pty Ltd, Brisbane.
The main influences on Melbourne’s weather are the low pressure system south of it, the high pressure system to the north-west, and the cold fronts to the west and east.
Warm front advancing from west to east behind the cold front. Note the lower atmospheric readings on the isobars.
Low-pressure system. Note
how the isobar is joining points with an atmospheric pressure of 992 (lower than the 1013 average).
FIGURE8 Symbols commonly used to show wind strength
calm (0–2 km/h)
3–7 km/h
8–12 km/h
13–17 km/h
18–22 km/h
23–27 km/h
33–37 km/h
38–42 km/h
28–32 km/h
43–47 km/h
48–52 km/h
53–57 km/h
TOPIC9 Water in the world 313
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