Funny Looking Cloud

Growing clouds in the afternoon slowly invading & taking over the blue sky. This is a typical scene in the afternoon during these weeks. I always like to look at the clouds because sometimes it would appear in certain shape that look like something we familiar with, bird, dog, human face, rabbit, etc. (well, may be one day I will see an UFO :-) haha) This afternoon, something unusual caught my eyes (don't worry, not UFO ;-p ), a portion of this cloud does not seen lumpy but smoothened like a half circle. I am not expert in weather observing, this may be just a very normal natural phenomenon, but I find it's quite funny looking.