How to model radiation cloud on a computer?

I'm a high school student with computer science experience, and I want to do a project simulating the movement of a radiation cloud, depending on three factors. What I'm thinking right now is having the user input these three factors (wind speed, etc) and drawing the radiation cloud a grid which represents a map of the world, then clicking a button to see how it moves. I would really like to figure out how to model this. Do I use an applet in Java or is there something a little more tailored to my project! THANK YOU SO MUCH!