I have flown almost that exact route in a c210 and distinctly remember one wet season (2000?) being forced lower and lower down to below 500 feet under cloud with two big black columns of water from cells many miles wide each side of my track. It was north of the Fitzmaurice. I was heading for the gap between the rain columns - where it was light on the other side. It was getting darker and darker under the thunderheads, I felt like a moth to a light.
As I got closer, two huge lightning bolts arced into the ground in the gap, and it seemed to narrow quickly. Bugger this I thought.
I still had an out behind me - and the fuel - and turned around getting buffeted by the blast coming out the bottom of the cells. I headed south and then picked my way eastwards then northwards getting to Darwin with an extra 0.8 on the tacho.
RIP fellow flier.