This is the 478th most frequent Norwegian word.
nordlige
"Northern."
Here, 'nordlige' is an adjective modifying 'delen' to specify which part of the country is being referred to.
Jeg bor i den nordlige delen av landet.
I live in the northern part of the country.
In this instance, 'nordlige' describes the origin or orientation of the 'vindforhold'.
Nordlige vindforhold dominerer i denne årstiden.
Northern wind conditions dominate this season.
Here, 'nordlige' qualifies 'områdene' to describe their geographical location.