Jupiter reached Opposition at about 1am UT on the morning of 3rd December 2012. Here are two images of different aspects of the planet. The one with the GRS was taken on the night of the 3rd and the second image taken on the 4th, with slightly better seeing conditions.
Opposition means that the Sun, the Earth and Jupiter are in a line. The Sun is therefore shining directly on to the face of Jupiter as we look at it. It also means it is closest to us and hence the disc is the largest it gets in this apparition.