The gangsta nod

Ok, so I'm sure that there is some logical explanation for this, like he is just sniffing the air, but everytime I walk past Pook on his favorite spot on the back of the couch, he gives me the 'gangsta nod' as if he's saying "hey". It's the 'nod' where he lifts his chin up in the air once and then lowers it. A cool move, very fitting for the cool cat Pook. But quite funny.