nā

many or much. This is a modifier denoting quantity. In our sentence:

il ñamma anūri nā ā mūrāna masīrien
il ñamma jalūra rā sāen āñ nō ā marāona;

nā is modifying the collective anūri or wind. Now we know:

Happening at the same time:
the North Wind is making lots of wind,
the wanderer is causing/doing something.