I'm writing a story involving a world with three moons. The third moon is small and distant, and by my calculations it has only a very minor effect on the world's tides (about 1.27 percent). The second moon, however, is large and close enough that when it's in conjunction with the first moon—which happens every 32 days, give or take—it would augment the first moon's tidal force by about 25 percent. How dramatic an effect would that have on the world's tides? Are we talking a minor coastal flood every month? A major coastal flood? A massive tidal wave that could scour away a city?

None of these numbers are set in stone. What I'm aiming for, ideally, is a second moon that causes just enough trouble that everyone sees it as a bad omen, but not so much that you can't have a maritime civilization.

ETA: Although the second moon passes in front of the first about every 32 days, it doesn't do so at the same longitude. That happens about every 14 months. In case that matters.