Last Thursday, when Minnesota was getting pelted with Tornadoes and Severe weather, a Tornado hit Northwest Rochester, MN. The storm cell that came into Rochester had a long history of producing Tornadoes in Dodge and Mower Counties, and when the cell came into Rochester a Severe T-Storm Warning was issued, the sirens however were activated in Rochester because of a report form a spotter confirming 70+ MPH winds. The news at the time, which was covering the storm, explained that they didn't know why they were activated

The sirens in the Northwest area of Rochester did not activate, and within a few minutes, an area in Northwest Roch had been torn up by a tornado that formed out of nowhere, of course.
Post Bulletin, our local newspaper, wrote an article explaining that there was a software glitch and that outdoor sirens are, again, an outdoor warning device and not to be relied upon indoors.
http://www.postbulletin.com/newsmanager ... 2&a=458014
It irks me that reading the few comments on the article, people blame the person in charge of activating them for all of the problems. Software is never flawless, and it certainly wasn't operator error. On the other hand, it goes to show that even though Olmsted tests their sirens weekly and continuously monitors them, even the most comprehensive system can fail.