First, the idea that a tornado can't hit a big city is one of those dangerous myths that can be deadly. Similar myths say that a river, a lake, a hill, or some other kind of landscape protect certain places from tornadoes. Strong tornadoes come from huge thunderstorms that go where the upper-altitude winds push them, including across cities. As you note, a tornado hit downtown Nashville, Tenn., earlier this spring. This year's February tornadoes in Florida, which hit late at night, started some local officials there talking about the need to install sirens.
Sirens are a way that reaches everyone.
Even better are weather radios that turn themselves on when a warning is broadcast. But, few people have these. I would think that before deciding to do away with the sirens, the city council should hear what the local emergency management officials and the National Weather Service have to say. I'm interested in building a tornado shelter for my family. I recall seeing on a television news magazine in the past year a story about a university in Texas that had produced a plan on an above ground safe room built out of block and rebar.