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Favorable winds over Japan carrying radioactivity out to sea

Posted by: JeffMasters, 2:16 PM GMT on March 16, 2011

If there is going to be a major nuclear disaster with massive release of radioactivity into the atmosphere from Japan's stricken Fukushima nuclear plant, today would be the best day meteorologically for this to occur. The low pressure system that brought rain and several inches of snow to Japan yesterday has moved northeastwards out to sea, and high pressure is building in. The clockwise flow of air around the high pressure system approaching Japan from the southwest is driving strong northwesterly winds of 10 - 20 mph over the region. These winds will continue through Thursday, and will take radiation particles emitted by the stricken reactors immediately out to sea, without lingering over Japan. Since high pressure systems are regions of sinking air, the radiation will stay close to the ocean surface as the air spirals clockwise over the Pacific. The contaminated air will remain over the ocean for at least five days, which is plenty of time for the radiation to settle out to the surface.


Figure 1. Surface weather map for 8am EDT today, taken from the 6-hour forecast from this morning's 6 UTC run of the GFS model. A high pressure system to the southwest of Japan, in combination with a low pressure system to the northeast are driving strong northwesterly surface winds over the country. Image is from our wundermap with the "Model" layer turned on. The lines are sea-level pressure (blue contours, 4 mb interval) and 1000 to 500 mb thickness (yellow contours, 60 m interval). Thickness is a measure of the temperature of the lower atmosphere, and a thickness of 5400 meters is usually close to where the dividing line between rain and snow occurs.

Thursday night and Friday morning(U.S. time), the high pressure system moves over Japan, allowing winds to weaken and potentially grow calm, increasing the danger of radioactivity building up over regions near and to the north of the nuclear plant. On Friday, the high departs and a moist southwesterly flow of air will affect Japan. These southwesterly winds will blow most of the radiation out to sea, away from Tokyo. Southwesterly winds will continue through Sunday, when the next major low pressure system is expected to bring heavy precipitation to the country. Beginning Thursday night, the sinking airmass over Japan will be replaced a large-scale area of rising air, and any radiation emitted late Thursday through Friday will be carried aloft towards Alaska and eastern Russia by this southwesterly flow of rising air.

Ground-level releases of radioactivity are typically not able to be transported long distances in significant quantities, since most of the material settles to the ground a few kilometers from the source. If there is a major explosion with hot gases that shoots radioactivity several hundred meters high, that would increase the chances for long range transport, since now the ground is farther away, and the particles that start settling out will stay in the air longer before encountering the ground. Additionally, winds are stronger away from ground, due to reduced friction and presence of the jet stream aloft. These stronger winds will transport radioactivity greater distances. I've made trajectory plots for the next three days assuming two possible release altitudes--a surface-based release near 10 meters, which should be the predominant altitude in the current situation, and a higher release altitude of 300 meters, which might occur from an explosion and fire from a Chernobyl-style incident. Given that the radioactivity has to travel 3000 miles to reach Anchorage, Alaska, and 5000 miles to reach California, a very large amount of dilution will occur, along with potential loss due to rain-out. Any radiation at current levels of emission that might reach these places may not even be detectable, much less be a threat to human health. A Chernobyl-level disaster in Japan would certainly be able to produce detectable levels of radiation over North America, but I strongly doubt it would be a significant concern for human health. The Chernobyl disaster only caused dangerous human health impacts within a few hundred miles of the disaster site, and the distance from Japan to North America is ten times farther than that.


Figure 2. Five-day forecast movement of plumes of radioactive air emitted at 10 meters (red line) and 300 meters (blue line) altitude at 18 UTC (2pm EDT) Wednesday, March 16, 2011 from the Fukushima Daiichi nuclear plant. The plumes spiral clockwise around the high pressure system to the southwest of Japan and stay near the surface. Images created using NOAA's HYSPLIT trajectory model.


Figure 3. Five-day forecast movement of plumes of radioactive air emitted at 10 meters (red line) and 300 meters (blue line) altitude at 18 UTC (2pm EDT) Thursday, March 17, 2011 from the Fukushima Daiichi nuclear plant. The plumes initially spiral clockwise around the high pressure system to the southwest of Japan and stay near the surface. By Saturday, though, the plumes get caught in a southwesterly flow of air in advance of an approaching low pressure system. Ascending air lifts the plumes to high altitudes, where winds are stronger and rapid long-range transport occurs. Images created using NOAA's HYSPLIT trajectory model.


Figure 4. Five-day forecast movement of plumes of radioactive air emitted at 10 meters (red line) and 300 meters (blue line) altitude at 18 UTC (2pm EDT) Friday, March 18, 2011 from the Fukushima Daiichi nuclear plant. The plumes get caught in a southwesterly flow of air in advance of an approaching low pressure system. The plume emitted near the surface (red line) stays trapped near the surface, but the plume emitted at 300 meters is lifted to 3.5 km altitude by the rising air associated with the approaching low pressure system. Images created using NOAA's HYSPLIT trajectory model.

Resources
Seven-day weather forecast for Sendai near the Fukushima nuclear plant

The Austrian Weather Service is running trajectory models for Japan.

Current radar loops from the Japan Meteorological Agency

Rare subtropical cyclone forms near Brazil
An unusual low pressure system that came close to becoming a tropical storm is in the South Atlantic, a few hundred miles east of the coast of Brazil. The Brazilian Navy Hydrographic Center has officially named the system Subtropical Storm "Arani", but I'm not sure the low would have been named by NHC, since Arani has somewhat of a loose circulation and limited heavy thunderstorm activity. The storm is expected to move slowly eastward out to sea, and does not pose a threat to South America. The latest run of the GFDL model shows little development of Arani, and the storm is now encountering a frontal system, which is bringing 20 - 30 knots of wind shear. It is unlikely that Arani will become a tropical storm. Some runs of the GFDL last weekend were predicting Arani would intensify into a Category 3 hurricane; that's the first time I've even seen such a prediction for a South Atlantic storm. The metsul.com blog has more info on Arani, for those of you who read Portugese.


Figure 5. During the daytime on Tuesday 15 March 2011 at 1820 UTC the TRMM satellite flew over a rare cyclone labeled Arani in the South Atlantic. Arani had the appearance of a tropical cyclone but has been classified as a subtropical cyclone. NOAA's Satellite and Information Service classified Arani as a T1 on the Dvorak intensity scale which would indicate an estimated wind speed of about 29 kt (~33 mph). TRMM's Microwave Imager (TMI) and Precipitation Radar (PR) data were used in the image above to show rainfall near Arani. Image credit: NASA.

Jeff Masters


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Trace radioactivity from Japan likely over the Western U.S. today

Posted by: JeffMasters, 2:11 PM GMT on March 18, 2011

Traces of radioactive substances emitted by Japan's damaged Fukushima nuclear power plant will likely arrive over the Western U.S. today, carried by the prevailing west to east winds that have blown over the Pacific Ocean during the past week. Rainfall is expected over California this weekend, and it is likely that the rain will wash radioactive particles out of the air to the surface in quantities that will be detectable at several locations. I want to strongly emphasize that the radioactivity from Japan arriving over the U.S. over the next few days poses absolutely no threat to human health, and is present in only miniscule quantities. The radioactive plumes from Japan have had seven days to dilute over a 5000+ mile journey, and have been subject to deposition to the ocean due to gravity and rainfall along the way. Natural radiation is present in our environment every day, and the extra radiation from the Fukushima nuclear plant will cause much less than a 1% increase this background radiation. Radioactive particles from the Chernobyl disaster in 1986 were detected in North America ten days after that event, and caused no harmful effects. The radiation from Japan over U.S. during the next week should be at levels even lower than the Chernobyl fallout.


Figure 1. Backward trajectories for the air arriving at the surface (red line) and 300 meters altitude (blue line) in San Francisco, California on Saturday, March 19, at 11am PDT. According to the latest run of the GFS model, the air arriving in San Franciso tomorrow will have originated near the surface in northern Japan last Saturday, when radioactive emissions from the Fukushima nuclear plant began. The radioactive particles arriving in California will be in trace quantities, and will have no harmful effects on human health. Images created using NOAA's HYSPLIT trajectory model.

Radioactive plumes emitted from Japan's troubled Fukushima nuclear power plant continue to move offshore to the east over the Pacific Ocean today, thanks to predominantly west winds blowing at 5 - 15 mph. These winds are being driven by the clockwise flow of air around a surface high pressure system centered just southeast of Tokyo. As this high pressure system moves northeastwards, parallel to the Japanese coast, today through Saturday, winds will gradually shift to the southwest, keeping the radiation from the Fukushima plant blowing out to sea. As the winds shift to southwesterly, the sinking air over Japan will be replaced by rising air, and radioactive emissions will begin being lifted high in the atmosphere. Since there is less friction aloft, and the high speed winds of jet stream increase as the air moves higher in the atmosphere, this radiation will undergo long-range transport. Latest trajectory runs using NOAA's HYSPLIT model (Figures 2 - 4) show that radioactivity emitted today could wind up over Alaska after five days, and radioactive particles emitted on Saturday could make it to California by late next week. I've made trajectory plots for the next three days assuming two possible release altitudes--a surface-based release near 10 meters, which should be the predominant altitude in the current situation, and a higher release altitude of 300 meters, which might occur if there is an explosion and major fire. However, the 5-day trek to Hawaii and California is 4000 - 5000 miles, and a tremendous amount of dispersion and dilution of the radioactive plume will occur. Given the current levels of radiation being emitted, any radioactivity reaching Hawaii or the U.S. may be difficult to detect, and will not be a threat to human health. Keep in mind also that the most dangerous radionuclide to human health in the radioactive plume--Iodine-131--has a half life of eight days, so will be reduced by at least 30% after 5 days of travel time.

Of much greater concern is the possibility of dangerous level of radiation over Japan. The next period of onshore winds that will blow radioactivity inland over Japan may occur beginning on Saturday night (U.S. time), continuing through Sunday, according to the latest run of the GFS model. The latest HYSPLIT trajectories show winds on Sunday may carry radiation from the disaster site southwards over Tokyo. A low pressure system is expected to bring considerable rain to Japan on Sunday, and this rain is likely to remove most of the radioactivity from the air where rain and radioactivity are both present. The winds associated with this low are difficult to predict at this time, since the winds will be light and variable.


Figure 2. Five-day forecast movement of plumes of radioactive air emitted at 10 meters altitude (red line) and 300 meters (blue line) at 18 UTC (2pm EDT) Friday, March 18, 2011 from the Fukushima Daiichi nuclear plant. The plumes get caught in a southwesterly flow of air in advance of an approaching low pressure system. The plume emitted near the surface (red line) stays trapped near the surface for 4 days then lifted to 4 km, but the plume emitted at 300 meters is lifted to 5 km altitude after 2 1/2 days by the rising air associated with the approaching low pressure system. Images created using NOAA's HYSPLIT trajectory model.


Figure 3. Five-day forecast movement of plumes of radioactive air emitted at 10 meters altitude (red line) and 300 meters (blue line) at 18 UTC (2pm EDT) Saturday, March 19, 2011 from the Fukushima Daiichi nuclear plant. The plumes get caught in a southwesterly flow of air in advance of an approaching low pressure system and lifted to 4 - 5 km altitude. The plumes are predicted to move over California and Mexico at high altitude. Images created using NOAA's HYSPLIT trajectory model.


Figure 4. One-day forecast movement of plumes of radioactive air emitted at 10 meters altitude (red line) and 100 meters (blue line) at 18 UTC (2pm EDT) Sunday, March 20, 2011 from the Fukushima Daiichi nuclear plant. The plumes get caught northerly winds, and the two lower altitude plumes move over Tokyo by 6 UTC on Monday, March 21. This is a low confidence forecast, as winds are expected to be light and somewhat variable on Sunday over Japan. Images created using NOAA's HYSPLIT trajectory model.

Resources
Seven-day weather forecast for Sendai near the Fukushima nuclear plant

The Austrian Weather Service is running trajectory models for Japan.

Current radar loops from the Japan Meteorological Agency

Jeff Masters


Joined: Oct 1999
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FAUX NOOZ.....

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All from the Huffington Post - a real good news source. frown

Ann Coulter with a rebuttable from Bill O'Reilly, gee he is from Fox News also isn't he?

Shep Smith (quite liberal) makes an arguable point.
Limbaugh -- He does Satire doesn't he?
Glenn Beck -- misspeaks but immediately corrects himself with a very arguable point.


Jim
Formerly from somewhere on a beach in Belize

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