At the heart of Jenna Blum's second novel, "The Stormchasers," is a touching read about a complicated sibling relationship, with thoughtful analogies about the storms of human emotion and actual storms.

But you'll have to weather some drizzle to get there: more than 100 pages of clunky dialogue, forgettable characters and overwrought plotting.

Karena, a Minneapolis newspaper reporter, has an estranged twin brother, Charles, whose fast-cycling bipolar disorder comes with a tornado obsession. After a missed encounter on their 38th birthday, Karena sets out to find him on the stormchasing circuit.

When we finally meet him, about 180 pages in, it's a relief. He's our one real character, from his head banging as a preschooler to his reckless insolence as a teenager. Blum's even got his manic rants nailed, down to the spit that collects in the corners of his mouth when he fast-talks. Scenes where Karena bears witness to Charles' medicated fogs and tortured anguish come from an obviously compassionate and knowledgeable writer who understands families and mental illness.

The way Karena and Charles swirl each other would have been enough to whip up a powerful book, but they also have a shared secret. The real energy is in Charles and his understanding of his illness -- he believes he is the human form of tornadic activity. This character and Blum's artful construction of storms-as-signifier for the way Charles and Karena handle fear are the electric aspects of the book.