Why shillong is rainier than kolkata?

Shillong lies at a higher altitude than Kolkata. Due to the presence of the hills, the Bay of Bengal branch of the Southwest Monsoon gets obstructed, resulting in a heavy shower on Shillong. Also, Kolkata is situated to the west of Shillong. The rainfall decreases from east to west in North India. Hence, Kolkata gets less rainfall than Shillong.