The speaker looks back at someone they once expected to be a huge, life-altering force. A tornado tears everything up and leaves nothing the same, and that is what they braced for. The poem's turn comes in the third line, "But I wasn't right," which is a quiet admission of a misjudgment. The person turned out to be "more of a storm."
What makes the poem interesting is how small that correction is. A storm is still powerful, still loud and unsettling, but it passes, and life afterward looks much as it did before. The speaker doesn't say whether this was a relief or a letdown, and that leaves the feeling a little ambiguous. The tone seems calm and reflective, maybe wistful, with a hint of disappointment under the plain wording. The short lines and simple language make it read like a thought the speaker is just now admitting to themselves: the person mattered, but not in the way they had imagined.