$('.cloud').each(function(){
var cloud = $(this);
function move(){
mL = Math.round(Math.random()*60);
mT = Math.round(Math.random()*60);
// set callback upon complete animation
// set easing to linear to prevent acceleration and deceleration of animation
cloud.animate({left: mL, top: mT },2000,'linear',move);
}
move();
// get rid of timer
});