I cycled around Australia including Darwin to Perth. Here is my web page for 19491km of Australia cycling in 2001:
http://www.mvermeulen.com/oneyear/australia.htm
If your question is about prevailing winds, then I found the wind roses at BOM to be helpful:
http://www.bom.gov.au/ Be aware however that these are just prevailing winds. I had some wonderful tailwinds going across the Nularbor but also some strong head winds as well.