Sorry but this is not a good idea. This would require knowing where the people are that are being notified. Your tv, radio, and most phones already do this, and it is good enough. How would you tell nostr users about a tornado in Kansas without knowing which nostr users are in Kansas? This would create an attack vector.
Discussion
Have you ever followed emergency and public service alerts on twitter? You just choose what services you your self are interested in subscribing to and get those tweets. You can set it to notify you so it shows up in your notification tab and you get a push notification. But what ones you get are entirely based on who you choose to follow.
I've never used Twitter. And those services don't know where you are and no one can see the notification pushed to your client? By logic alone signing up for a push notification for events in a city would probably tell others where you are. That can defeat the anonymity nostr provides. I'll stick with my NOAA radio and antenna tv.