hey i got psnumai as well and i have to say it is the biggest resource hog plug in i ever used i mean to render out 5 seconds of a ocean took me well over a hour i was baffled .. but other then that , if i was you id use particles for the rain drops trapcode people website has a file for download with some good rain with drops hitting a colliosion point and breaking up . id start thier for the rain . the sky you could use fractal noise that should do the trick . or just take video of sky and put it in 3d space and move it above the ocean kinda flattend out .
the easiest way to do lighnting is make a adjument layer . mask it on the sky and lil over the water and then keyframe the bright5ness to jump for one frame or so . u could also throw in the cc lighting effect in ae i think its cc not sure but its in thier somewhere