Tropical Cyclone Information for the Australian Region
Check that out, a Cyclone that cuts right thru the middle of Aus back in '95.
Craven, I'm not so sure if "because its less than 1000, it's a cyclone" is quite accurate because you get plenty of low pressure systems with a central pressure lower than 1000 that do not form as a cyclone, I think they just get referred to as a tropical low. However it is probably quite correct to say that you wont have a TC with a central pressure near 1000hpa.
Sea surface temperature is one of the biggest factors to forming and sustaining a TC- as mentioned, above about 26C and you have the right stuff. Shear is also a key part.
BoM site has a lot of info about the hows and whys.
We've got some pretty warm seas this year, so far the season has been quite active- expect a few more before it ends!
Would have been interesting if Bianca crossed as an active cyclone down near Perth. She dropped a bit of water along the Pilbara.