This java-based interactive calculator shows the distribution of fallout, by wind, from nuclear bomb blasts of various yields. The contours depict calculated radiation doses of 300, 25, and 1 REM at 96 hours after detonation.
In using the calculator, you may select from an assortment of virtual satellite maps of major world cities. You may select the magnitude (15, 30, or 45 miles per hour) and direction of the wind. You may choose from an assortment of yields ranging from 1 kiloton to 50 megatons. And, you may choose the location of the bomb blast on the map simply by clicking on the preferred location.
The calculator requires that you have java installed. It can be found here. [Note: Images may take a little while to load.]