Air Trajectories from the Fukushima Nuclear Power Plants. by Kenneth P. Bowman, and Cameron R. Homeyer at Texas A&M University. From the site:
The maps on this web site show the approximate motion of air that has passed over the Fukushima Daiichi and Fukushima Daini nuclear power plants at various times. These plants were damaged by the strong earthquake and tsunami that occurred on Friday, March 11, 2011 at 05:46:23 UTC in Japan. Please be sure to read this page, which explains more about how the calculations were done, as well as their limitations and uncertainties.The purpose of these maps is to give a general idea of where radioactivity might go in the days following a release.Please note: we do not have any direct knowledge of how much radioactivity might have been released from the plants or when it was released. We only know what we can gather from publicly available news sources.
All the trajectory maps can be found here.