Winds are expected to remain eastward through the morning of Friday March 25 Japan Standard Time (JST).
Reports continue of troubles at the reactor site. Wednesday morning there was a radiation spike at reactor 2 and later Wednesday black smoke was emerging from reactor 3. Both incidents caused workers to evacuate the site. As emissions continue at the reactor site the greater and more widespread radiation values are probably a result of the wind patterns Tuesday March 22 that moved the plume toward Tokyo (see post for 3/22).
Examining the revised plume forecasts (these latest ones ran 1 day after Update 6, and so include observational data closer to the forecast time) we see that during the southward phase of the plume extension late Wednesday afternoon (JST) there were periods of time when coastal areas of Japan around the city of Choshi might have been impacted by the plume. (Compare the images below to the corresponding times in the 3/23 post). This type of variability (in this case, between forecasts started at different times) is a hallmark of coastal regions. A method to use that variability to generate more accurate plume forecasting was described in this prior post.