This cloud is called Asperitas. They are possibly formed by downward drafts. Pictures 1 & 2 are from the web and the 3rd photo was an attempt by myself while in Stanthorpe. It was in 2017, a fairly warm day for winter then a cold front started to move through and the temperature plummeted by 8°C. I only caught a glimpse of it while driving along a dirt road and by the time we hopped out of the car most of it had vanished.





And my attempt. I think I have a better one on the cameras SD card. I have so much photo sorting to do.