"exploding comfortably" - oxymoron showing the ease and calm with which nature can be violent and destroy; also shows the speakers colloquial comfortability with the state of the island
"spits like a tame cat turned savage" - simile showing that nature can always turn on you, it cannot be tamed or controlled
"huge nothing we fear" - one could consider the Troubles a huge nothing (basically just Christian in-fighting), and yet the consequences were massive
iambic pentameter, conversational
single stanza to show the isolation of the island
enjambment on lines 3-9 shows the speed the storm comes in, caesura at the end to show the painful anticipation of the next
free verse to show the limitless uncontrollability of the storm
semantic field of the violence of nature: "blast", "pummels", "bombarded"
semantic field of war: "strafes", "salvo", "bombarded"
the storm is an extended metaphor for the Troubles in Ireland (Stormont the Northern Irish Parliament, double entendre in the title)