Here’s a preview of a possible color-scheme for the mountains on the Māinm map. Red and yellow denote dry mountains in rain-shadows, the others are wet mountains that get rain-fall, or don’t impede rain-fall, or which cause rain-shadows.
The wind patterns on Māinm are relatively simple: no coriolis force, for one, which means no wind bands. Usually the wind travels towards the Sun, which warms up most the bits it sails over, and the east-west corridor more than north-south: lots of centerward winds.
Why the giant desert in the east (left)? The sun rises in the ocean right there, so the water is really hot. So hot, that it creates a low pressure area that is stronger than that of the desert itself: that, plus the land-mass to the west, and the mountain ranges north and south means there are no wet winds towards the desert.
The eastern sea is hotter than the western sea due to sea currents. Which are all caused by the giant maelstrom at the center of the world, that sucks in water, sends it into the underworld, where it falls “down” a mountain into rivers, then back into the sea. So, all currents are towards the center: and the eastern seas are dominated by currents from the center towards the north and south, warming up the eastern coast of the continent. Similarly, the western coast and ocean are cooled down by the currents then passing through the icy seas in the north and south.