northern vs northerly

northern is not a noun while northerly is a noun.

Word	Noun	Adjective	Verb	Adverb
northern	No	Yes	No	No
northerly	Yes	Yes	No	Yes

As adjectives, northern and northerly are synonyms defined as:

As adjectives, northern and northerly are synonyms defined as:

northern (noun)	northerly (noun)
	a wind that blows from the north

northern (adjective)	northerly (adjective)
situated in regions of the north	coming from the north; used especially of wind
in or characteristic of a region of the United States north of (approximately) the Mason-Dixon line	oriented toward the north
coming from the north; used especially of wind
oriented toward the north

northern (adverb)	northerly (adverb)
	in a northern direction