Why is Australia mostly desert?
I'm working on the map for the world my DnD group is going to be playing in, and half of the continent they're starting on is similar to Australia in the way that it is mostly desert with some places that are pleasant. Here's a link to the country they're starting out in:
(I've since then fixed the river, added some towns, another forest, and a marsh)
The country is completely enclosed by the mountain range, I'm wanting on the other side to be a desert, a big one at that. The country is similar to England in weather
1) What makes Australia so much desert?
2) Is my continent plausible? Could it exist?