The two major sounds in Michael Cook's Jacob's Wake are the radio and the storm. Thematically, the radio's function is to allow the audience and players to know what is happening outside the house: the raging storm, state of emergency—the real world. These bits of information reflect the chaos in the house: from the hymns to the dire warnings of danger.
The storm thematically represents the deterioration of the Blackburn family. As the storm's strength and violence escalate, so does the hate of this fractured family. Functionally, the storm creates a rising sense of suspense and impending doom.
There are bad feelings between most of the family members. Almost all of them hate each other, even while they form unholy alliances to carry out actions that show just how morally destitute they are. The only "pure soul" seems to be Rosie who tends to each family member and tries to keep peace. Winston is a man who lost the will to search for meaning in his life:
What else could I ha' been, Rosie? What else could I ha' done?
As the family disintegrates with anger and resentment, the storm increases. Brad (the preacher) is revealed as the father of Mildred's illegitimate baby: both frozen to death (some years before) hidden outside the Blackburn house. The brothers demoralize each other. Wayne even tells Mary to stop nagging him, a departure from the regard he shows her.
One sure sign of impending disaster takes place when Alonzo insults Mary:
I've just lost me stripper down to the Blue Flamingo Aunt Mary. Me and the boys was wonderin' whether ye was any good with a bottle.
This goes beyond teasing Brad or fighting with Wayne: he has spoken crudely to his elder, and worse, to a woman. Rosie, uncharacteristically, smacks Alonzo across the face.
Their world is upending itself. The radio fades in and out with updates; then it reports that the government has resigned—spelling disaster for Wayne. What do any of them have to cling to? For only Winston and Rosie have each other. None has anywhere else to go.
As the storm nears a climax, a couple of things happen. First, Mary insults Rosie.
The sins of the parents come home to roost.
Mary tells Winston he and Rosie have contributed to Alonzo's "moral ignorance." Winston warns his sister not to blame Rosie for anything, alluding to Rosie's "holiness," and how Mary has no concept of holiness. But Mary insults Rosie again:
Holiness. I'd prefer to call it childlike sympathy.
Winston throws a bottle across the room, clutches his chest and drops to a chair, sure his heart is failing him. Second, Winston discovers the forgery of his signature to have Skipper committed to the asylum. Wayne and Alonzo have tried to drive Skipper out, and blemished Winston's name. He wails:
My name! 'Tis all I've got left.
He goes berserk—gets his shotgun and loads it as he stands in front of his wrecked family—his sons and sister. The storm takes the lights, and Winston opens fire. It was one decent thing he might have done (he says), but he missed everyone.
The radio dies. The storm—"snow and ice and hurricane combine[d]" —represents the family. Where they have tried, the storm succeeds and destroys them. Skipper's ghost says:
Comes a time when things has to be brought together as best they kin. When ye has to steer into the starm and face up to what ye are.
The men come together at last, following Skipper's orders—and face the end united.
The thematic function of the storm in Jacob's Wake is that the storm represents the metaphorical and symbolical occurrences that are happening between the family members and within each family member as they get more and more remote from calm order and break more and more of the rules of social being resulting in increasing chaos, just as the storm breaks the rules of orderly nature resulting in increasing chaos.