Winter tends to be the best time for flying in most of Oz - except for the S.E. corner ie Tassie!
Winter is characterised by a large high over the continent with typical anticyclonic weather. Don't forget the reversed flow direction in the S. hemisphere.
Also winter sees frontal systems moving across the southern part of the continent, moving from W to E.
Summer sees the ITCZ move down to lie across the north of the country so tropical TS are the order of the day across the top end.
The general southerly movement of the pressure systems tends to push the fronts further south lessening their influence.
Spring & Autumn are somewhat transitional. There seems to be a tendency to strong westerlies around Aug/Sep.
Oz bureau of met has a website that might help. I think it's <a href="http://www.bom.gov.au" target="_blank">www.bom.gov.au</a>
Hope this helps.
[ 22 January 2002: Message edited by: Tinstaafl ]</p>