On each, I’ve plotted two types of data: pressure and wind speed and direction.

Pressure values are shown with isopleths — lines connecting points of equal value. On the surface maps, they show sea-level pressure (like the barometric pressure you get in your daily weather forecast). Pressure values are given in millibars (mb) using a two-digit shorthand. The two-digit numbers that begin with 9- through 7- would actually be 99x, 98x, or 97x mb of pressure. (Average sea level pressure is 1013 mb.) Two-digit numbers that begin with 0- through say 4- have 10 as a prefix, so pressures would actually be 100x through 104x mb of pressure.

On the upper-level (850 mb and 500 mb) charts, they show the elevation of the relevant pressure value in meters. On these charts, the 850-level usually lies somewhere between 1,200 meters and 1,600 meters in elevation. The 500-mb level usually lies between 5,100 meters and 5,900 meters.

Wind blows from areas of high pressure to low pressure. On a flat, non-rotating Earth, the wind direction would be perpendicular to the pressure isopleths. In the real world, rotation of the earth and friction against its surface causes an apparent deflection in the wind direction: to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. This apparent deflection — the Coriolis effect — is what causes clockwise circulation around high-pressure cells in the Northern Hemisphere (counter-clockwise circulation in the Southern Hemisphere) and counter-clockwise circulation around low-pressure cells in the Northern Hemisphere (clockwise circulation in the Southern Hemisphere).

That’s the theory of wind, but other factors can influence wind direction locally, thus the wind barbs are needed. Think of the wind barbs as arrows indicating wind speed and direction. The direction of the “fletching” — the feather-like bits — of the arrows indicate the direction the wind is coming from. The length and number of the feathers indicates the wind speed. More information on how to interpret the wind barbs can be found here: http://www.hpc.ncep.noaa.gov/dailywxmap/wxsymbols.html and here: http://www.hpc.ncep.noaa.gov/dailywxmap/plottedwx.html#dd

It’s not unusual for winds to blow in one direction at the surface and a different direction aloft. Likewise, wind speeds tend to increase with elevation because the effect of friction with the Earth’s surface decreases with height.

Radioactive isotopes tend to be heavy, so if the stuff is not blasted high into the atmosphere, airborne contamination is likely to stay in East Asia. Ocean currents may carry isotopes across the North Pacific, however, so effects on aquatic life will depend on how much is spread, how far its spread, and where it eventually settles. If there’s an explosion — such as at Chernobyl — isotopes can be blown sky-high (literally) and can be transported thousands of miles by air currents.

Forget what some of the government- and industry-approved talking heads tell you: in a worst-case scenario, radioactive fallout can reach North America. Here’s a link to some modeling from the Austria’s weather service: http://www.zamg.ac.at/aktuell/index.php?seite=1&artikel=ZAMG_2011-03-15GMT08:26

-30-