Fukushima: Latest maps of spread of radiation plumes in Asia-Pacific - March 18, 2011 ( Central Institute for Meteorology and Geodynamics, Vienna, Austria)

Declan Butler has a blog entry entitled: Fukushima Crisis: Latest maps of spread of radiation plumes in Asia-Pacific - March 18, 2011. From that entry:

Wind directions in Japan are currently blowing radiation from the troubled Fukushima nuclear power plant eastwards out to the Pacific Ocean (see Figure 1), but a shift in directions Sunday risks sending the radiation plume towards Tokyo (see Figure 2). These models have just been published in a bulletin by Austria's weather service, the Central Institute for Meteorology and Geodynamics in Vienna.

On the colour scale, red represents 100 millisieverts per hour (100 mSv/hr), and purple a maximum of 100 nanosieverts per hour (.0001 mSv/hr). For an explanation of the units see "Radiation exposure, beyond the numbers". In terms of dose, an exposure of 100mSv is enough to slightly increase the chances of developing cancer later in life; a dose of 100 nanosieverts is neglegible.

All the maps are here.