MODIS/Terra satellite January 24, 2007, 2:10 UTC.

 

The clouds formed from an afternoon T/S near Australia’s tropical northern coast.

 

At the top of this convection system, the air ceased to flow upward and spilled out into an expanding ring.

 

There appears to have been relatively constant wind through a deep layer of the atmosphere, allowing the uplifted air to spread out equally in all directions. The outflowing air may also have disturbed and amplified existing clouds, making them more reflective. Increased reflection of sunlight makes the clouds seem more brightly white to the MODIS sensor.