upwind vs leeward

upwind is not a noun while leeward is a noun.

Word	Noun	Adjective	Verb	Adverb
upwind	No	Yes	No	Yes
leeward	Yes	Yes	No	Yes

As adverbs, upwind and leeward are synonyms defined as:

upwind (noun)	leeward (noun)
	the side of something that is sheltered from the wind
	the direction in which the wind is blowing

upwind (adjective)	leeward (adjective)
towards the side exposed to wind	on the side away from the wind

upwind (adverb)	leeward (adverb)
in the direction opposite to the direction the wind is blowing	away from the wind
away from the wind