Javascript & CSS Expert needed for small animation task2

I have a psd for the website shown below [login to view URL] it has circle of icons, i call it as cloud there are several clouds shown what i want is to write a javascript/jquery/css script to animate the clouds coming from top to bottom at any time one cloud shown in the middle, one in the top as if starting to fall down and one in the bottom starting to collpase inside... basically the clouds scroll down automatically with smooth animation...when ever user keeps mouse over the clouds pause and when clicked we either show light window or take to inner page these clouds go continiously in a loop.. the animation should be smooth not browser cpu intensive..should be leight weight and simple.. when page is resized then automatically clouds get adjusted based on the size of the window and clouds should come from random position in the top expert in javascript and css could do this in an hour...or less (so bid if you are only expert)