Yeesh... first "nai" means yes, now "notos" means south... gotta keep an eye out for these words that mean the exact opposite of how my English ears hear them.
I had the exact same problem when i was learning english with νότος(=south)-north and αριστερά(=left)-right!
I agree. I have to tell myself it's the opposite of what I am thinking.
Βορρέας does not exist. Βοριάς is used as βορράς in every day speech, denoting the wind (also τραμουντάνα) as well as the direction or point on a compass. The adjective northern, north is βόρειος