About The Weather Charts

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About The Weather Charts

Chart Levels

Surface charts are labelled "MSL" for Mean Sea Level. Upper air charts are labelled with the pressure level in hectopascals (hPa) e.g. 500 hPa. Note that pressure decreases upwards in the atmosphere e.g. the 250 hPa level is higher than the 500 hPa level.

Timestamping

Some charts are timestamped in "UTC" (Coordinated Universal Time) or "Z", which are equivalent to GMT (Greenwich Mean Time). To convert these times to local Australian times, add the time difference between your Australian time zone and GMT to these times:

For Eastern States, add 10 hours e.g.: 0000 UTC = 1000 (10 a.m.) EST
1200 UTC = 2200 (10 p.m.) EST
1800 UTC = 0400 ( 4 a.m.) EST next day
For S.A. and N.T., add 9.5 hours e.g.: 0000 UTC = 0930 (9.30 a.m.) CST
1200 UTC = 2130 (9.30 p.m.) CST
1800 UTC = 0330 (3.30 a.m.) CST next day
For W.A., add 8 hours e.g.: 0000 UTC = 0800 (8 a.m.) WST
1200 UTC = 2000 (8 p.m.) WST
1800 UTC = 0200 (2 a.m.) WST next day

Don't forget that daylight saving adds an extra hour to the difference between Australian times and GMT. So, during daylight saving, the difference for New South Wales, Victoria and Tasmania is 11 hours instead of 10, and the difference for South Australia is 10.5 hours instead of 9.5.

Updating

Some charts are updated every 3 hours, some every 6 hours, some every 12 hours, and others every 24 hours.

Validity and Issue Times

The "valid" time is the time for which the chart is valid; the "issue" time is the time at which the chart is issued. "Analysis" charts are a snapshot of the weather situation at the valid time, while "prognosis" charts are a forecast of the weather situation for the valid time.

Caution - Getting the Latest Chart

If your browser uses caching (i.e. it keeps a local copy of items you view), don't forget to use the "Reload" or "Refresh" commands in your browser to ensure you get the latest chart. This also applies to forecasts, warnings and satellite pictures available on this service.

August 1995

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