Persistent offshore winds have aided the heroic efforts of nuclear workers to protect Japan from radiation exposure. For the past week, except for a very brief period when Tokyo measured elevated radiation levels, winds have been blowing radioactive particles out to sea. Because of the favorable winds, most of Japan, except for the area in the immediate vicinity of the stricken power plants, has observed radiation levels close to background levels. However, the winds are quickly changing now. Radiation will soon blow towards Tokyo.
The major population centers of Japan reported near background radiation levels on March 20, 2011.
Spinach, leaf vegetables and milk withing a radius of 100 miles of the reactor site may have suffered contamination, but Tokyo has been spared by favorable winds. Because iodine -131 has a half life of 8 days, the iodine contamination of milk and spinach is a short-term problem. Reports of contamination of milk and spinach 90 miles from the reactor are concerning but this radiation appears to pose little long-term risk.
As Japan edged forward in its battle to contain the damage at its ravaged nuclear power plants on Saturday, the government said it had found higher than normal levels of radioactivity in spinach and milk at farms up to 90 miles away from the plants, the first confirmation that the unfolding nuclear crisis has affected the nation’s food supply.
The restoration of stable power to reactor 2 is a huge step towards regaining control of the damaged reactors.
Japan's quake-hit Fukushima Daiichi nuclear power plant saw a stable source of electricity finally reach one of its crippled nuclear reactor building Sunday, a key step to move ahead in restoring the reactors cooling functions to avoid the disaster from worsening further.
However, a low pressure area developing in the sea of Japan is going to turn winds onshore taking particles from the power plants onshore towards the west, then north, before they may finally be blown offshore. This model run was done by me using NOAA's online trajectory model.
Then, as a front pushes through and high pressure develops to the north of Japan, winds will shift to the north east, blowing particles towards Tokyo.
Dr. Jeff Masters, founder of Weather Underground, did a similar model run yesterday.
Here's his expert assessment.
By Dr. Jeff Masters
Published: 8:17 PM GMT on March 19, 2011
Radioactive plumes emitted from Japan's troubled Fukushima nuclear power plant will remain near the plant or move out to sea today, due to weak offshore winds blowing over the region. On Sunday, an elongated area of low pressure will develop off the southeast coast of Japan, and the counter-clockwise flow of air around this low may bring several periods of north to northeast winds Sunday through Tuesday to Tokyo and northern Japan. According to the latest trajectory plots from NOAA's HYSPLIT model, these winds may be able to transport radioactivity from the Fukushima power plant to Tokyo beginning at 18 UTC on Sunday. The low pressure system will also bring periods of rain to Japan Sunday through Tuesday, and these rains will tend to remove the great majority of the radioactive particles from the air in a few hours, and it is uncertain how much radioactivity might make it to Tokyo. Radiation at the levels being reported coming from the troubled plant are not high enough to be of concern to human heath outside of Japan, so I will not be posting further plots showing the long-range path of the radioactivity unless there is a major explosion resulting in a significant increase in radioactive emissions. From what I've been able to gather from official reports of radioactivity releases from the Fukushima plant, Tokyo will not receive levels of radiation dangerous to human health in the coming days, should emissions continue at current levels.
The heroic sacrifice of the Japanese nuclear workers to rapidly regain control of the power plants may have come just in time. I'm hoping and praying that they continue to gain control of the damaged facilities.