Looking over NW Australia atm, you can see intense concerntration of lightning under the system, with a large circular anvil shield. Havent got my measuring tape out to check if its legal size *giggles*, but definitely an interesting feature.
See satellite images below
Formed on evening, from thunderstorms, and will probably last 6 hours. We get about 20 a year for the Australia region.
NB: Tropical Cyclone moving SE through Fiji visible on RH edge of IR sat.