An amateur astronomer in Australia was the first person to report the appearance of this black spot on Jupiter on July 19. Anthony Wesley from Canberra wrote on his online journal:
It took another 15 minutes to really believe that I was seeing something new – I'd imaged that exact region only 2 days earlier and checking back to that image showed no sign of any anomalous black spot.
Now I was caught between a rock and a hard place – I wanted to keep imaging but also I was aware of the importance of alerting others to this new event. In the end I imaged for another 30 minutes only because the conditions were slowly improving and each capture was giving a slightly better image than the last.
Eventually I stopped imaging and went up to the house to start emailing people, with this image above processed as quick and dirty as possible just to have something to show.