The user IS using Opus. Interestingly enough, the checkerboard system is very common in the area in which he is flying (Houston, Texas). The clouds will begin as looking thin with less condensation and water built up within them; they will look something like this photo. As the clouds begin to become more thick and filled with water, it is not as easy to realize the checkerboard pattern with the naked eye, but in reality the condensated "cores" of the clouds are still aligned with each other in a checkerboard pattern. The weather radar is able to pick up these densely precipitated cores of the cloud as the red color.